I would only be okay with this if they were perhaps small story arch campaigns sold, like they had in recent years on FFXI. Also always charge full price for the game. When new expansions come out bundle it with original game but retain the $49 pricetag. Would that be enough to recoup costs? probably not. Expect to pay I just hope its no more than 10 a month. I think some subscriber games would be much more successful if they cost less per month