I'm looking to *add* to my collection, and I have cash to do it with, but reality is that those people who think their machine is worth more now than it was when it was NIB, and it's not NIB (sometimes *seriously* so!) are smoking crack.
There's been a crazy amount of bone-smoking going on in this "hobby" the last couple of years. Reality is that these are electro-mechanical devices and they deteriorate. Playfields, plastics, electronics, wiring, mechanicals. If you replace all of the above and it's back to NIB condition then it's worth a NIB price -- at the time it was made!
I've bought two NIB machines and two prototypes. One of the prototypes has some little niggles; it's my Safecracker. I love that machine and will never sell it, but it's.... unique. The other is a No Fear. I also own the two Pin2K games, both bought NIB straight out of the back of the factory dock when I lived in Chicago. My RFM has something like 2500 plays on it, according to the audits, and it's accurate -- the PRISM card hasn't had to have its battery replaced (yet.)
I've had others that have come and gone, and presently one of the "come" is Apollo 13, which I got at a reasonable price. It was pretty screwed up electrically and mechanically, but in terms of playfield and plastics it's in good shape, cabinet is good, translate is fine and it had no acid damage. One TIP122 was blown up (literally blown up) and a few other minor board problems were present, but those were reasonably-easy to fix and it was filthy, so it required a near-complete strip-down, and Sega doesn't make that easy. If you had paid someone to fix all the mechanical and electrical things you'd have been into it for a solid 2-3 days worth of work, or a couple of grand at reasonable labor rates plus parts.
What's that game worth in the market *before* that work? $800, 900 maybe? Yep. What did I pay for it? Guess. It's 100% now mechanically and electrically, I redid the GI and controlled lighting in LED the way I like it, fixed the board, electrical and mechanical issues (of which there were many) and just converted the flipper mechs to Williams baseplates and mechanicals. It now plays *better* than new (for that reason) but it's still not worth more than the NIB price, because it simply isn't better than new on-balance.
You want to try to sell me a half-screwed Addams Family for $4k? Go right ahead and try -- but you're not getting my money. That's more than the NIB price which means it needs to be *better* than new, and you know damn well it's not -- they never are, and on Craigslist that's especially the case.
There's a half-dozen machines I'd pay somewhere close to NIB prices if they're in somewhere close to NIB condition. Addams Family is one of them. One of the others is Funhouse. But look -- I can LED a machine for $100 all day long, the way I want it done, so to me the value in such is zero because the way you did it is probably not the way I want it, which means it's worth zero to me -- and even if it *was* the way I'd like it the value is still small, because the cost of doing it is small. It's that simple when you get down to it.