I've been thinking lately that an attacker who accumulated over 50% of the network would currently find it highly unprofitable to do double spends. And since you can't short BTC an attacker with 50%+ might want to disguise the fact he controls that much to keep the value from dropping but I don't think they would try any double spends. In the real world with the current valuation of BTC it isn't likely that you can find enough victims to make up forgoing the huge profits of generating 1/2 of all BTC currently mined. Also any large transaction would be delayed by hours if not days so it gets even harder to do a double spend even with 50%+. What are your thoughts?
I mainly agree with your arguments regarding a 51%-attacker who wants to 'make money' with his attack.
BUT, don't forget the other potential type of attacker, who want to destroy Bitcoin and doesn't care about making money out of double spends etc.