I feel sorry for OP. I don't think OP was trying to stir a pot, etc. To me it sounded like "Hey, which ride would be the most valuable if there were a black market for fp's?" DH and I have done this a ton of times.
Christmas shopping, when we walk out to our parking spot to leave we joke about how we could probably get $20 for our spot.
I recently purchased the last t-shirt at my daughter's gymnastics meet and thought to myself "Boy, if I auctioned this off, what would I get?"
I have the feeling that's the frame of mind OP was in when posing the original question.
My answer is that under the old system, when a fastpass could be used anytime after the "window", I'm thinking Soarin', TT, TSM would be good money makers. Those are the parking spot up front in my previous analogy.
Problem is under the new rules, you'd have to find a buyer before the return window closes which limits your options.
I have given fast passes away before. Arrest me. Although I almost was arrested as the family I gave them to looked at me like I was completely insane, trying to scam them. But I couldn't bring myself to throw them in the trash.
I probably wouldn't sell them, as they didn't cost me anything in the first place. But it's FUN to imagine.