Quoted from shacklersrevenge:

There are two groups of buyers.
There is the uneducated, played it on pinball arcade, gotta have it, I'm 40-50 and I'm bored and need something to do or collect and mod, deep pockets, no problem with the price, If thats what they're asking, hell, that's what I'm paying, group.
Then there is the pinball player, the die hard that loves the game. They are patient, know some people that can hook them up, they look under the rocks, hunt, and from time to time buy the games they want for hundreds and sometimes thousands less than price guides created by the above group.
The first group drove prices to the moon, and expects the second group to ride that rocket. I personally never went for that cosmic ride.