Examples of (but no "get-rich") paid membership sites?
headstorm: What about metafilter.com?  I haven't joined, but I read their content daily.  They charge a one-time membership fee of $5, which allows you to post a question on ask.metafilter.com once per week.  Members can comment on anything they desire, leading to many diverse niche questions being answered by 'the hive'.  They do supplement their revenue by google text ads, however.