Well, you'll need to give us some more details; is it from a reputable manufacturer (Brunswick, Diamond, etc.), what was the value of it new, how large a table (7 foot, 8 foot or 9 foot)? A one inch rip in the felt is enough to make refelting the table necessary, so that will lower the value. Are you selling any equipment with it or just the table? What's the quality of the rest of it? Are there nicks or gouges in the wood, do the risers in all four feet still work, is the leather in the pockets torn or faded?
Given the abundance of cheap pool tables on Craigslist, you may have difficulty getting 500 for it, but if it's a nice championship series full-size slate table in good working condition (apart from needing the refelt), $500 could be a steal. Alot of the cheap tables on Craigslist have wood tops instead of slate, which drastically lowers the value.