I agree that she provides a sufficient amount of income, but after seeing the sales provided by Naked Songs . . . Of course, it was a fantastic album, but many fans constantly complain that they don't like Aya's mature style. For some reason, they can't face the fact that Aya isn't into bubblegum pop anymore, and she's not going to jump into R & B like Goto or go heavy on guitar riffs. Personally, I think this is a style that suits her. Why push her into something she doesn't like doing? And, obviously, she's very happy to be working with her friend (agreeing with roninbuddha here), so I don't think she's getting ripped off in this deal.
Tsunku concentration on GAM is probably because it's what fans wanted, and they're both very popular. We all assumed that it would stay a solid unit if their sales were decent, and they've proved to be that way so far. While it's nice to have both of them together, I see how everyone is a bit upset that Aya is lacking solo music, yet Miki is still releasing with MM. I'm also sad, because I want some more Aya solo music, but I am content that she is at least releasing music in some form or fashion, even if it is within a unit. Perhaps after this whole GAM thing, she'll release a new single. *positive thinking*