I agree that I may lose some users forever. But surely there is a point at which it would become profitable. Maybe 15 minutes is too short?
Obviously the goal is to convert users who are slightly interested in the upgraded features but not enough to chance it on a pricey membership. I’m confident in what the site offers, and if I can get them in for $1 I think I can keep them.
The real answer is probably to test it. But I’d like to have a strong hypothesis before starting a test.