Your suggestion seems to be to sink items. I don't think sinking items to up their market value should be necessary.

Old items become worthless over time, and there is no point in buying those from the ToriShop, as they are ass cheap on the ToriMarket. But the newly created items, mainly 3D items or the new colors, will be popular and interesting to get. The only way to buy those items when they are first introduced is through the ToriShop.

A clever marketer will have to focus on those new items, and let the old items be. It's gonna be difficult for them in the state between waiting for commerce on the new items to take place, and seeing the prices of the old items drop which makes those old items very hard to sell. Once the commerce of the new items happens, marketers will be able to make profits again. It's a matter of patience.

So a better solution for the problem you described would be for the Item Forgers to keep on a constant supply of new items that are worth getting. This is enough to keep people interested in saving up for them, as well as purchasing them through the ToriShop and keeping the market fruitful. I think the Item Forgers are currently doing a good job regarding this.

Also, if we were to sink items, how do you suppose we sink items without getting more tc in circulation? Perhaps a scrapping system, similar to what tf2 has, might be an option. I can't think of other decent ways to sink items.