https://www.gamespot.com/articles/get-extra-cash-for-trade-ins-at-gamestop-for-a-lim/1100-6460768/

If you've ever traded in a game at GameStop (or most other places), you probably got two offers: one for how much cash they'd give you for the game, and one for store credit. When it comes to trade-in values, cash always gets the short end of the stick. But between now and August 12, for any items you trade into GameStop, your cash offer will be boosted up to the same amount as the credit offer. If you like your currency to be usable anywhere, now is a good time to take the money and run.

How much you'll get depends on the item you trade in. GameStop accepts trade-ins for games, consoles, accessories, and even electronics like phones, tablets, and smart home devices. You can use the search bar on this page to find out what your items are worth as a GameStop trade-in on any given day. (Amazon and Best Buy have similar pages you may want to check to ensure you get the best deal.)