I would like to see something like a price check app that bloops up when looking at ebay listings. I don't know if I'm explaining that right, but as an example say you're looking at a Super Mario Bros. listing on ebay for $15, the plugin would bloop and be like "we have this item valued at $5 and rising" or whatever

There are a lot of results in the eBay Game Sniper tool that are incorrectly matched. For example, a listing explicitly stating it's for the Xbox 360 version of a game being matched to the Xbox One version in the tool. Listings for demo discs and loose manuals are also often matched as the actual game. If refinement of the tool is planned in the future, it might be beneficial to start compiling a database of matches flagged as incorrect, which we could add to by using a "report" button.

I pulled a German SIR card and I would like to track the value on this site aswell. When adding this feature, gradings like from AOG could be added to the site aswell. The german market isn´t that small due to 3 german speaking countries which print german cards.
By adding this feature it is ensured that people in germany can track their whole collection. (because most people buy english/japense/ or german only)

Btw. The German SIR goes around for 290-500€ and the same card in english for 240r€

Add One Piece Japanese TCG 

I think Mercari should be used to check prices against in the market as they are becoming a heavy hitter for resale.

Create a tool for users to create a custom set or list.  Then let users collect against that list and see what they have in their collection and what they don't have yet.

Examples: a list of all licensed NES games, Mega Man home console games, games published by Konami, etc.

It would be great to have a button on each wishlist item to move it to your collection. Right now, the only way to (indirectly) do this is by clicking on the wishlist item, then clicking "See Historic Prices" on the item page, then finally there's a button to add it to your collection. This would make updating your wishlist much more convenient and would also give that tiny endorphin rush from "completing" an item of your wishlist.