Ask HN: User choice subscription rates

I was wondering if there was a service that allowed the subscriber to choose the price of their subscription to a website? For example, if you wanted to pay $5 for pro membership per month you can do that or if you only wanted to pay $1 you could do that. I'm not sure I will go along with this plan, but the idea has me intrigued enough to see if it's possible. Thanks in advance HN.