More people want the base games so they can restore them. So demand goes up, but the supply doesn't. So the price goes up. If someone bought a brand new playfield and is looking, a few hundred extra dollars probably won't stop them at that point, so the price goes up. That game will be more desirable because more people want it, so the price goes up. At some point it hits a peak where too many people won't buy the crappy base game because it is too high, and we have found the top of the market for a beater with a blown out playfield.