What most people fail to realize is that 51% does not mean BTC will suddenly drop off the face of the internet, nor will ghash be able to freely take coins as if a big button appeared for them as they crossed it.

They've also stated several times that they do not want to cross that line, as even if they did break bitcoin and give themselves a huge amount, who will buy it? Inflation such as that caused by a successful 51% attack does not cause a steady price - it would crash the moment they crossed the line, meaning they would get nothing out of it and the bitcoin community would be crippled, not something ghash wants considering they make most of their money from people trading btc!