Quoted from fosaisu:
A number of owners have had persistent and recurring issues, so a Lebowski that's plugged along without significant problems is worth a premium
There is no reason that this game won't have issues after the money's spent.
This game is $20k because it's about pride of ownership and bragging rights, not because it is problem free and unbelievably fun.
You still can't hide the fact that it's just a pinball machine.