I can understand that reasoning, and it does make sense to me too, but only if all the money goes to the park. Ideally then even only for successful applications.
Ideally you should have an option to support the park even if you don't go/don't want/can't go for a hike and in any case you should receive a clear breakdown of the costs in what goes where.
It made sense to me, as I was under the impression that the money went directly to the park. But the fact that it goes to a middleman changes things.