There must be a set Jagex "lower limit" price for each of sinked item. If we figure out what that is, and only buy when the price is below that, there is always a powerful force for the item to go over that price.
As of now, my estimates could be too low, because item sink is limited to certain amount per day, and we are sitll in early stages of price correction.
Also, one fault with the tax is that the Grand Exchange is not a fair market. People don't know the bid/offer beforehand, which is a fundamental difference between GE and fair market systems, so some of the economic theories will be less efficient.
Another thing I was thinking about is how this item sink adds a super artificial demand for items, it's a hugge gp generator for those specific items at the cost of all other items sold in the ge - ideally, ALL items should be sinked for it to be fair
How can we profit from this fact? Basically only deal with items on the item sink list, and there is massive profit to be made
Prediction of the Jagex price of item sink items:
Abyssal bludgeon: Armadyl godsword: 12,000,000 - 13,000,000 Arcane sprit shield Spectral spirit shield Armadyl chestplate Armadyl chainskirt Bandos chestplate Bandos tassets Dark bow: 780,000 - 800,000 Dinh's bulwark: 13,000,000+ Elder maul: Armadyl godsword Bandos godsword: 12,750,000 - 13,250,000 Saradomin godsword Zamorak godsword Kodai insignia Kraken tentacle Nightmare staff and Orbs (Eldritch, Harmonised, Volatile) Occult necklace Arcane prayer scroll Dexterous prayer scroll Torn prayer scroll Saradomin sword Scythe of vitur Smoke battlestaff Toxic blowpipe Trident of the seas Twisted bow Zamorakian spear: 18,000,000 - 19,000,000