He is refering to "The Wish Economy" developped in the Tomes series by Frank Trollman & co.
Yes.
Essentially, since goods like diamonds and gold pieces, and all magic items worth less than 5000 gp(the limit on what you can create with wish), are easily reproducible, while items worth more take actual effort to make, there's no way in hell you can buy an item worth more than 5 grand for gold, since the wizard/artificer who made the item can probably just print gold at will. So a schism is formed between the markets for items worth more and less than 5 grand, and stuff like souls and liquid pain and the like, that cannot easily be mass produced, is used as currency to buy stuff on the expensive side of that barrier.
Please bear in mind that my tone is genuinely inquisitive here and not condescending / sardonic.
Is this relevant? We will have people who, aside from mass printing GP, can mass-produce any other mundane material. We will have two cohorts, who are item-crafters. One can make whatever, but has to worry about GP / XP, though the mundane material costs are irrelevant, and can drain the XP from the mass-producible items. The other doesn't have to worry about GP / XP, but is slightly more limited in what he can make.
So we are self-sufficient once we get together, right? So, why would it matter what means we would use to get items from others, if we can get them all from each other, setting the terms each time in between the players.
Don't get me wrong, however the NPC's want reimbursed for their wares / services is entirely up to you, and I won't object to anything you set forth as far as such for this world. I just don't see it being relevant except in rare circumstances like trying to get a Doppelganger Brain, which would be completely ad-hoc anyway.