If I were to rent my points I would also ask for more than the usual $15-17 pp.
Imho prices has gone up just look at the buyin costs and annual dues.
If you just put up your points for rent then maybe $16-17 pp would be ok. If you have a hard to get reservation then $20 is also okay. I see it like this, if the renter saves 40% compared to renting direct then $20 pp is fine.