Educate your friend as best you can before he goes (too bad you couldn't go with him). I went with a friend that was buying a MK1. The seller told us before we got their that it was "all original". The seller was asking $300 or $350. Got their and it was in a 19" cabinet, clearly not "original". I opened it up and it was missing a few minor things, like the test switch, the bezel was from some other game just turned around (more evidence of not original), and the monitor had some burn in from the previous game. I told my friend to use these points in negotiating. He asked the guy if he would take any less than what he was asking, the guy said $250 and before I had a chance to let a word out, my buddy jumped on it. I think he could have gotten him talked down to $200, maybe even less. My friend was just so ---Bad words, bad words, whatcha gonna do? Whatcha gonna do when saint censors you?--- excited to get an arcade machine, he wasn't thinking about actual value. The more your friend knows before he checks it out, the more likely he'll be able to get a fair deal. And tell him to keep his cool, if the seller won't sell it for a fair price, there are plenty of other arcade games out there.