The bubble will burst at some point. It rose predominantly because people my age opened arcades, arcade/bars with nostalgia for the 1980's and that era of games. The pay by the hour model became like the pay by the ounce frozen yogurt stores that popped up everywhere a few years back (of which very few have now survived). The arcades want popular games, naturally for their public facing venue so the Froggers, DKs, Galagas, etc all rose in price from an average of like $400 to $800-$1000 or so now for an average to slightly above average game with no issues. The rare games have always been valuable as a collector niche, the Major Havocs, iRobots, whatever. So now you have both the common games increasing in price (somewhat dramatically) and the rare games holding their price...for now.
The recent arcade fad will be replaced by something else new at some point, the older collectors will become too old to repair games and their knowledge will be only available on internet forums/posts and those that have kids probably will end up just selling their galaxian cabinets as their kids gravitate to whatever latest technology hits the market.
Tl/dr, arcade game prices will bottom out as new arcades close down with supply heavily outweighing demand at that point. I haven't followed too many dedicated arcade hardware attempts on TG or whatever but I imagine any lack of new score attempts on dedicated hardware has more to do with a lack of a mainstream driving force of curiosity (King of Kong for example) than it does the fact that hundreds of people are searching but can't find/afford a dedicated Bubbles machine. Those Bubbles fans are the truly sadistic anyway.
