This is a really interesting idea. I liked it a lot, both flavor-wise and as a way to balance melee with magic, until I started reading the descriptions of individual materials.
First, are you aware that, with this rule, 7000gp gives you equipment which is more powerful than 20 levels of some melee classes? A 20th level commoner with a relicwork pure iron sword and relicwork pure iron armor is significantly more powerful than a 20th level fighter, barbarian or monk with a ten times that value in magical equipment. For that matter, a 20th level commoner with a non-masterwork pure iron dagger and non-masterwork pure iron splint mail could hold his own against PC classes.
A 20th level commoner only has 10 Bab. They cannot benefit from relicwork abilities.
Even with nonmasterwork, how dangerous are they? The basic pure iron dagger is hiting for 1d6+10, the splint mail is granting +15 AC and 5 hardness. The commoner still has 1d4 HD for life and all bad saves. It just doesn't drop if you breath its way, but will still handily drop to a pimped charger. Even if the 20th level PC just stands there the commoner will need dozens of turns to wear down the hundreds of HPs the high level PCs should have now.
Pure Iron
Standard weapon: This requires knowing your target's BaB, which takes information away from the DM. I suggest making this based entirely on numbers the player actually knows. Also, adding extra math like this will slow down the game.
Relicwork: Now you're almost guaranteed to completely disable a spellcaster of higher level than you, provided you can get a full attack (easy with ranged weapons). How do you disable someone's mouth without killing them anyway, or asked in a better way, if your sword strike is that precise, why not just stap them through the eye and kill them?
Relicwork armor: So you get mettle and evasion. I'm not sure whether this is unbalanced, but it will sure annoy DMs.
I like the special ability of pure iron. In traditional fantasy and mythology, iron is the bane of extraplanar creatures such as fey and demons. Maybe you should work more off that theme for the weapons, having extra affects against fey and outsiders.
That's for what
cold iron is for.
Standard-The DM doesn't have to give you the enemy's Bab, he just has to say if your attack roll is a crit threat or not. Much as you can gauge an oponent's AC by power attacking for diferent amounts. Anyway it makes sense that a skilled warrior could gauge an opponent's martial skill.
Relicwork-cannot be combined with fullattacks (only standard action or charge, both explicitly limited to one attack). Also eyes are pretty tiny targets protected by the eye socket and one that the owner will instinictively protect, in particular you'll always see it coming. Disabling mouth is simply a matter of smashing/cuting someone's jaw off.
Pure Silver
Artifactwork weapon: So basically, you auto-hit with every attack, if the target has at least as many HD as you. This might be a little much, even for 350,000gp.
Meh, not really, ACs in the 40s- 50s are pretty common for optimized PCs/enemies by those levels.
Geting some form of wraithstrike will probably be cheaper and just as efficient.
Masterwork armor: Immune to ability damage and drain. Seems like a lot for 3500gp. Maybe instead, you suffer half ability drain/damage, or there's a 50% chance of it failing?
Relicwork armor: This is balanced enough, but it's strange. Why would a non-magical item make you immune to fear?
Artifactwork armor: You might want to explain this better. If it blinds creatures with darkvision, then shouldn't it shine really brightly? That means that, while you blind such creatures, they always know where you are. Ooh -- what if, while blinded, they can only see you? Everyone else is just too dim to see. That could be an interesting effect.
Again, I like the special effect.
Masterwork-You'll need both the shield and armor to resist ability damage (7000 GP), and then heavy armor (full plate will run you an extra 3000 GP) to resist ability drain. Notice also that not everybody gets default heavy armor or tower shield proficiency.
Relicwork-Being clad in shiny awesome silver-white plate can do wonders for your self confidence.
Artifactwork-It's suposed to be more along the lines of "It is so pure it burns us precious!", overwhelming the senses of dark creatures. Didn't you see Lord of The Rings?
Cold Iron
Standard weapon: So for as little as 1gp, you can make a spellcaster completely ineffective. Preventing defensive casting is an epic feat. Given the power level of this rule in general, I can accept that, but also vastly increasing concentration DCs makes this too powerful, in my opinion.
Phantasmwork weapon: Maybe okay for 350,000gp, but this could grind the game to a halt. Every time you're struck, you have to figure out your AC and effects without spells, powers, and spell-trigger items.
Standard-The basic defensive casting rule is one of the most nonsensical things in 3.X (defensive casting against Lancelot the 20th level paladin is as hard as Bob the 1st level thug). They can still 5-feet step away from your or whatnot, or gain cover/concealment, or one of their million other tricks. But at least they can no longer just stand in front of you taunting while casting as long as they somehow focus really hard.
Phantasmwork-You're telling me you wouldn't have your base/unbuffed character statistics readily available?
Masterwork armor: These powers are interesting but pointless. No one in a world with this rule will use magic armor, since pure metal items are easily a hundred times more powerful for the same cost.
Artifactwork armor: Completely disable all spellcasters in a 60 foot radius at will. If you have a melee-only party (which is very likely, given this rule), there will never be a spell, SLA or SU ability used in a dungeon crawl, where most rooms will be smaller than 120' from end to end.
Phantasmwork armor: What is a permanent spell turning? What happens when you use up the turned levels? Does it renew instantly? If so, then you might as well say the character automatically turns all spells. Does it renew as a standard action? Once an hour? Once a day?
Masterwork-Guys with spellcasting (rangers, paladins, clerics, gishes, wizards with mythril stuff) will still want magic armor obviously. Animated magic shields will still be used by those wanting to two-hand weapons for extra offense. If nobody got the ranks and feat to craft it in the party, geting hold of pure metal armor will prove tricky as well. Then there's also exotic magic weapon/armor abilities you may want to pick.
Artifactwork-Hmm, ok, reduced the radius a bit.
Phantasmwork armor-Renews automatically at the start of your turn, meaning it can still be overloaded in a single turn.
Special: The school of divination is now obsolete. Every city with 140,000gp will be protected by a permanent divination blocker. Every home owner with 200gp to spare will have their home protected. Every enemy will be protected.
Maybe rich people can get some privacy in D&D now. Commoners in their farmlands probably can't afford it still. Also the protection can still be ruined by simply disrupting one of the pieces, meaning you can have adventure and intrigue around agents send to disrupt a city's pure metal defensive measures.
I'll stop here, because I don't have time to review the other metals. Basically, I think this is a really interesting idea. It creates a world where spellcasters don't rule. Rather, they lead exceedingly risky lives, and must protect themselves at all costs, preferably with a hoard of level 1 commoners with 1gp pure metal daggers. It's a world where every warrior is a legendary fighter, and every wizard is a cowering figure, grasping at power. I wouldn't want to use your rule for any old game, but it would be an interesting thing to try out for a special campaign.
Thanks!
Now if you were to weaken the abilities, making them 2-3x as powerful as magic items of the same cost instead of hundreds of times as powerful, this could be an interesting rule to apply to a wider range of campaigns.
To be honest, in one hand I believe you're both overstimating a lot of the pure metal abilities, on the other magic weapons/armor are kinda overpriced as they are now. Basic armor protects against so few things while still limiting your max Dex and movement speed that most people just go with the light options. Having to pay thousands of GP just for just 1d6 more damage or +3 to hit is horrible as well. Spellcasters meanwhile get plenty of cheap efficient items to bolster their abilities such as scrolls, pearls of power, beads of karma, the list goes on.
This is a really interesting idea with a lot of potential, but it's too powerful as-is. You don't want a 10th level Commoner with a sword, armor and shield below his WBL beating an entire party of 10th level adventurers with magic equipment.
Commoners aren't proficient with armors or shields. Meaning they have to burn their feats to be able to use Pure Metal armor and shields. And even then they just have 5 Bab. So at 10th level they burned all their feats.
Now let's say the commoner 10 and a 10th level barbarian. Both have the same base elite array of stats, say 15 Str, 14 Con, 13 Dex, nobody cares about the mental stats. Let's put the 4th and 8th level boosts in Str and Dex for 16 Str, 14 Con, 14 Dex.
Commoner has pure iron fullplate, pure iron heavy shield (AC 31=10+1 Dex, +14 armor, +6 shield, touch 21, hardness 10), pure iron dagger+8 dealing 1d6+8), 10d4+20=45 HP
Tecnically speaking, the commoner autoloses because he's slugging around at 15 feet speed (in case he isn't even more encumbered by the weight). The barbarian just has to run away while throwing javelins or something. A caster could be flying in the air laughing while raining down death from above.
But let's say the barbarian is an honorable foe and charges head on. Feats are, say, EWP spiked chain, combat expertise, improved trip, weapon focus on spiked chain.
Has a +2 spiked chain and a belt of giant Strength +4, for a total of attack bonus +18, dealing 2d4+9.
Barbarian hits commoner's touch AC on a 3 or more (1+ if he charged first), probably making him tripped. Now maul down on the poor commoner. With hardness 10 he'll last a bit (barbarian needs just 9+ to hit the tripped commoner, deals average of 4 damage), but his chances of geting back up are basically nill. Even if he manages to get up and deliver an attack, the barbarian has 10d12+20=85 HP, DR 2 and AC 21 (10+2 Dex+7 magic Breastplate+1 ring of protection +1 amulet of natural armor). The commoner needs 13+to hit and will deal an average 9 damage. Tecnically the commoner is dealing slightly more damage, but is hiting less often, if he hits at all because he'll spend most of his time tripped, and the barbarian has basically double HP. And the barbarian still didn't even use his main feature, raging.
EDIT:
If you can get a pure iron dagger for 1gp, then it's common, whatever the fluff text says, and everyone has one. If it's uncommon, then the dagger costs more than 1gp.
I mean, hand-painted wooden dolls take skill to craft, but imagine if holding a hand-painted wooden doll made you virtually immune to all harm, and granted you the ability to dodge bullets, and could be used to heal wounds, and the going price was $20. You can bet that demand will be ridiculously high. Either they would be produced by the millions where labor is cheap, or the price would skyrocket, or governments would keep the secret closely guarded and send out armies with dolls to take over the world.
You just can't have a cheap but uncommon item in ridiculously high demand. Economies don't work that way.
Think of it more of a caster lobby. Wizards and clerics hate pure crafting, and they have superior communication/propaganda and travel/transport abilities. They're more than willing to make sure any merchant openly selling pure metal items has an "acident", and commoners in particular will meet awful demises if they're found with pure metal items in their possession.