This is marginally better than KnC, who's been stuffing every ASIC at hand in their Swedish facility guarded by buxom blondes with machine guns

Economically, I would not pay much more than 1.0-1.2 BTC per TH for ANY new miner. At present BTC rates, this puts the economically feasible price for the SP50 around $25,000 per unit.

Pay more than that, and you are unlikely to see any ROI - which is kinda the point of the whole thing if you are a professional operator with access to low cost electricity.
 
Everything comes down to price, price, price...