I will probably not buy anything above ~3 BTC for ~2.4Th/550-600W.
Depending on electrical costs and the avg price of BTC over the next year, 3 BTC (S&H included) is the max for that size of rig when you include the halving. A safer bet is 2 - 2.5 BTC.
1.5 BTC is more comfortable given the deluge of power that will hit the global hashing network when all these efficient devices hit the market.
Well its over 7 BTC. Twice the size we were anticipating.