I'd break it down this way:
$350.00 - $400.00 for the cabinet if its in good shape. If its an original US Red cabinet, it sahould be 25" not 19". Make sure the CP is in good shape, especially the overlay. If you don't like the Joysticks or buttons, ask for new ones (correct colors). Make sure the front and sides are RED with neo art work, not black with stickers. Also make sure the top 4 light pannels work. Check to see if the right power supply is in there. If its a Red US MVS cabinet, there should be a power switch inside the front coin door. This should work. Also, while in the front door, check the test button & free credit button. You might also want to check for coin mechs & coin bin to complete the machine. Lastly, get the manual!
As far as the games go, check what your choices are, then compare to Ebay Prices. If your only offered games that go on ebay for $10.00, then the $650.00 is too much. If you can get 4 games that go for $50.00 and more, then it sounds like a decent deal to me.
............Klaws buttrock