i think a hard limit is not a good idea, because it means somebody is planning the value of a post. Also celebrities would never post for a max of X.
However like i said i think like you the value needs to be spread better. There are certainly other ways to do it.
For me personally i have moved the needly up to $50 on a post, while my min seems to be $0.07. That is the difference that is too high. I would understand something like $0.5 to $3 or something in this range.
Well they have to find a solution, the rate of active users is going down, today it was 50%.