If Costco did not have such a friendly return policy I am sure Stern would be selling a bunch there to families that don't realize how hard it will be to keep the game playing well.
The truth is that the key customers for sustaining a business like pinball are repeat customers. The family that gets only one pin that they keep forever is not enough to make a huge difference in such a niche business. If those families get hooked and buy more then the manufacturers have something.
The new collector market is the reason Stern expanded their factory and JJP is able to make more games. Barcades also helped some.