why are there stocks all you can do is make it infinnity and make a sellback that removes 500-1000tcs from when you bought it?(long sentence)

The items in the shop have stock so that they can become rare.
Take hunter force/relax for example, their only 12k in the torishop but because their sold out and there are only ~100 of them you can sell them on the market for much more.
As a general rule of thumb items with qi rarely get restocked and items without qi do, though this isn't perfect for every item.

There isn't a sellback option on the torishop because that undermines the market and would make selling things to other people much harder.

Without stocks marketing would be extremely boring. Even if an item is cheap in Torishop the price can raise x10 if it has a low stock. Some items are meant to be hard to get.

oh ok thnx