Need to get rid of some item (or collection therof) forever?
Mantle of the Void is not the cheapest item (priced at just under 18.5k), but it's undeniably effective for this purpose. Normally, you're supposed to just use it to gain a +6 insight bonus on a single roll 1/day, with more uses gained by taking Wisdom burn. However:
If, for any reason, the wearer’s Wisdom is reduced to 0 while wearing the mantle, it swallows him whole and he disappears forever, unrecoverable even to effects such as reality revision.
So, for the cost of a sacrifice (doesn't have to be humanoid, a sheep probably works fine) and a way to inflict Wisdom damage/drain, you can send things off beyond the reach of Wish spells.
Now, this assumes that "swallows him whole" includes worn or carried items. The description doesn't mention other gear at all.
Also, for a second fun find is the Map of the Mind. Psychic Reformation 1/week for 16k. This is explicitly tied to the item, so having a couple of these lets you use it more often. Regardless, it's perfect for picking up crafting feats or similar "downtime" abilities.