More income isn't needed right now, and any possible benefits of an additional membership tier seem to me like they would be too superfluous. Maybe I'll do it at some future point, when more income is needed and/or I have some decent ideas for things that really should be payment-gated.

Don't worry about supporting the forum financially. The most helpful thing anyone can do is to just be a good member of the community by eg. helping newbies, patrolling for spam, or writing good posts.

P.S. Why do so many people read copper member as cooper member?