How do you check what your steam account is worth?

fwiw the licenses page includes every free weekend and giveaway you ever clicked, so even the paid total from that list isn't really what you spent. the purchase history is the honest number.

What you paid, or what it would cost today? Those are very different numbers. For what you actually spent, Account Details has your purchase history, and there's a page listing every license on the account. The calculator sites use current store prices, so every game you got in a sale or a bundle counts at full price and the total looks huge. And you can't sell a Steam account anyway, it's against the subscriber agreement, so the number is really just for bragging.