Quoted from ForceFlow:

What supporting evidence do you have? I know several people in their teens, 20s, and 30s who own games. Granted, not all of them are big spenders, but hobbyists can be any age.
Pinball is not just an "old guy" thing. Walk into any show these days and there is a fairly good cross section of the population flipping away--men, women, young, and old.

Quoted from BudManPinFan:

Wrong, that’s not how supply and demand works. When the number of buyers drops the prices will also drop or the pins won’t sell. The only reason the prices have risen to where they are is the increased demand.

Quoted from DaveH:

People started speculating on LE games. That's why they sold out so fast. Nobody wanted to miss the next Tron. But the games started to wane.

Quoted from brundaged:

Just putting this out there:
The Mr. Pinball Price Guide has been published for 28 years, and it shows that IN AGGREGATE pinball prices have appreciated by about 3% every year during that time.
Yes, individual titles have fluctuated significantly. And titles less than 15 years old tend to depreciate until they hit 15. I'm taking these statements directly from the Guide.
Shouldn't this hard data over nearly 30 years put to rest the idea that a crash in the pinball market is "inevitable"? At most, we might see a crash in NIB pricing, or in the pricing for pins less than 15 years old. But that's different than the bottom falling out of the market.
I still think the outlook for pinball is pretty strong.