the only sales you will make is if you have old classics from the 80s and back... all the good fighting games are a dime a dozen, maybe 100 bucks for the board to the right buyer, cabs are worthless... it's all about finding one in good shape and what you value it as... usually get them in nice shape from wholesalers cheap cuz they buy out big storage lots.
that was true 5 years ago... however 90s arcade gamers are getting into their 30s; and into financial stability and starting to buy up 90s era games... MK2 used to fetch $200 on a good day, now it's an $800 machine... a fully restored KI1 will earn you over a grand and TMNT, which seems to be the holy grail to 90s gamers went from being a nearly worthless machine to being one of the most valuable 90s era games.
It obviously varies depending on your location, and the nostalgia value of the games your selling but in general 90s era games are on the up and up in terms of value while 80s stuff has somewhat plateaued.
I'm sure in another 10 years or so we'll see 80s stuff start to devalue as collectors nostalgic for that era start getting out of the hobby and we have more people selling machines then there are new buyers picking them up. And then 10 years after that 90s stuff will start to devalue as well.
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As for MAME, MAME cabs generally fetch MORE than dedicated machines to non-collectors. People who just want a single machine for their "man-cave" and don't have the knowledge or drive to build something themselves will 150+ games for $500 and jump on it.
I had a beautiful Double Dragon machine. I couldn't sell it for $300 on Craigslist so I threw a 138in1 PCB in it and re-listed for $500... had it sold in 2 days then I sold the original game PCB for even more money on top of that. The guy who bought it didn't care that it was a Double Dragon cab he just saw an arcade machine in his price range with a bunch of games on it.