$3.50/mo.
I had AOL for several years until I got DSL. At that point, I switched to their bring your own access plan just because I was heavily invested in the email address (business cards with it printed, etc.), but was using no other AOL services whatsoever (why would you?). I had that for a year at around $15 a mo. Finally, I decided "it was time," called up aol's canceling department (which doubles as sales, it seems...They do not want to let you go). Well, the guy asks why I'm cancelling, and I muttered something about proprietary blah blah blah, and also that $15/mo for email only was ludicrous. He said something like "oh yeah, that is expensive," then told me about the service they offer (but don't bother telling anybody about) for that situation. Costs $3.50/mo. Email only & BYOA (I don't know if IM-ing qualifies as an extra service, but I didn't really care, either). I ended up telling him 'no' all the same (possibly out of spite for a year of 400% costs), but have talked to a lot of people using aol because they don't want to lose the email address. Spread the word..
Note: May have been either $3.95 or $3.00, I don't recall, but it's very close.