Craigslist is your best bet for arcade cabinets in your uber low price range. LA has quite a few listed constantly, but we're a huge area so if you live in a smaller city or in the middle of no where, you will undoubtedly not find much.
If I were you, I would just build my own cabinet with a cheap PC for mame/emulation, it can be done for very cheap if you're handy with tools. Sure, there are people out there with money to burn and waste on ancient arcade cabinets that only play a single game who "collect" these things, but people collect everything - different strokes for different folks I guess. I would much rather build my own with 1,000's of arcade and older system games personally.