I'm starting to think I'm crazy for spending 2.9 bitcoins on two Antminers only to barely be able to make 2.9 bitcoins
Bitmain always prices the miner at where the miners share a profit with us, though this is not any guaranty, but only intention, only educated guess for the future of mining difficulty. However, it seems that Bitmain's guess is better than those 25%~30% exponential assumption under which the difficulty fly out of the galaxy.