My methodology to get to the point of saturation:
1. Stalking. Research your local ops, make a point of driving by their shop. Be nice, be friendly, and await the inevitable dump of dead cabs.
Singular, usually, but sometimes they do spring cleaning. And doesn't hurt to ask permission. I think in my case they were glad to not have to lug oh, 3-500 pounds of equipment to the dump that ended up in my house, and much of that stuff is now residing in many member's games.
(have I made money from this? technically, yes, but it ends up being my parts fund, so.. no
2. Auctions. Useful for a few things:
Odd lots of stuff that only collectors want versus the population of Ops bidders interested in money-makers..
(who are you here, 'mushroom guy'? you bought my Centipede marquee
- I guess that falls under 'networking'..)
Good to get that ratty cab with some useful parts or a good start on a project. Galaxian cocktail=$20 out the door. Ratty, but salvagable.
Also useful as a 'reality check' for x game, so you can throttle back your investments in your own copy of said game. Or justify yours.
3. Craigslist. http://(yourcityname).craigslist.org/search/sss?query=arcade in as big a radius as you dare. Daily.
3 types reside there:
People with games that the monitor is dead/ wonky assume the whole game is worthless but for parts perhaps.
People who have games and assume that you want it to put on location or next to your restored Corvette $$$
Decent price, decent game. It does happen. Usually here.
I hit the 'make room! make room!' level with a #1 from CL. Home use only Atari vector needing a refresh kit and a corner
repair. I drove down there minutes after seeing the post, calling them, paying up, and telling them to remove the listing before..
well, somebody like me sees it. All she had so far, surprisingly, was an offer to buy the coin door.