I found these articles looking at the economics of sub-based MMOs and F2P / RMT-based MMOs interesting. They are just general evaluations - no specifics of who earns what - but it certainly makes the case for why more F2P MMOs are being developed than sub-based MMOs.
One interesting thing that sub-based MMOs are starting to do is offer additional, optional content for additional dollars. CoH/V's recent booster packs are one way that some MMOs are getting extra money from players who want to pay extra without necessarily excluding those players who only want to pay the basic subscription fee from any additional content (which would be the case with 'optional' expansion packs). Not everyone is happy with the booster packs, but it is certainly a way of getting access to the extra money on the table.