How much are real silver dimes worth?

As opposed to fake silver dimes, LOL?

A lot more information is needed. Silver dimes were minted at 4 different mints over a period of about 170 years so there's no simple answer without enough information to identify a specific coin.

As a rule of thumb most dimes dated 1940 and later that show even a moderate amount of wear are common among collectors, and sell mostly for their silver content - around 90 cents as of 09/2009. Older dates, as well as uncirculated and proof specimens, can be worth anywhere from a couple of dollars to many thousands. Please post a new question with the coin's specific date and whether it has a mint mark on the back.