Instead of just showing how much % expensive/discount an item listed is, maybe add a line under/next to it that shows the original Torishop price of an item?
Maybe when inspecting its page too, since it already has the prices for market sale/buy orders with the QI requirement [and arguably useless data of owned/traded recently since that is only relevant for rare collectible items] but lacks the Torishop's original TC & ST prices.
Would remove the extra click needed to check it on Torishop.

Also might be helpful to add the tax 10% under the marketplace_shop itself, with profits before and after tax deductions; with a a nice visual indicator showing one's premium subscription with date of purchase or expiration date, which would be reflected on their shop page.

Terrible HTML editing aside, it could also help with automatically showing the profit of a large amount of listings' before and after deduction without needing to manually pull up a calculator in Starbucks and calculate sales tax returns for a game's market.

Lack of categories to search within concerns me, but great work overall.