So basically if you buy lets say 10 GH from their website you are renting their mining equipment and you are getting same amount of BTC like you would if you bought 10 GH asic and mine for yourself minus fees?? So if you manage to sell your GHS at the same price you bought you have rented those hashes for free. In real life you would not be able to sell your $10K USD asic right away for $10K USD
But in real life $10K would buy you a heck of a lot more than 10 GHS.
Now I see the problem, Currently you can buy 600 GHs from butterfly labs for $4680 and you have to pay electricity cost. Same 600 GHs will cost around $8500 through cex.io - not a great deal, but I can imagine when next batch of asic miners will be shipped and GHS/BTC will fall that for few months this could be profitable