The price bubble won't entirely burst; A-list machines probably won't go back to the prices they were in, say, 2003. But there is a limit to how high they can go, because after a certain point, manufacturing reproductions becomes a no-brainer. MM is already near $15K. If it goes up to $20K, you could probably make a profit piecing them together by hand, using outside contractors for tricky stuff like custom metal parts (using CAD files). That demand isn't just going to sit there forever; it will be met one way or the other. That's where pinball machines are different from baseball cards and other collectibles. People who want a player's rookie card want the original card that was made back then, even though producing a perfect reproduction would be relatively easy and cheap. They care about provenance. I don't see any evidence that most pinball aficionados care about this, considering the number of mods, aftermarket PCB replacements, reproduction decals and playfields, and other changes made to games. A MM using the exact same parts as the original would fetch the same price; no one would care that it happened to be assembled in 2013 instead of 1997. And increasing the supply would eventually drive down the price to sane levels.

Games with licensed themes are going to be harder to commercially reproduce because of legal red tape, as are very complicated games with lots of toys. TZ and STTNG would be a real challenge because they fit both categories. And they're also not quite so insanely expensive yet. Monster Bash, though, is getting so high it might be worth it.

People who think pinball machines won't be reproduced now because they haven't been in the past are forgetting just how new today's prices are. $10K-$15K MM is a very recent phenomenon. We've seen prices on AFM and WH2O skyrocket just in the past few months. Reproducing machines didn't make sense when MM was the most expensive at $5K-$6K and most other A-list titles were near the $3K mark. But it is now starting to. That market demand will not remain unfulfilled indefinitely.