The SP50 would need to price in the range of 120-150BTC to compete
Surely you mean 80-90?

No way. Bitmain is selling 0.25w/gh at about 1.4btc/th.
This is 0.15w/gh and includes power supplies, but also a 'bulk priced' device, so i would expect 1.2-1.6btc/th.
That said, I'm not buying any hardware until my bitcoins are worth at least $300 again. Otherwise you will never earn back the btc you spend (like buying hardware with $100 bitcoins in mid-2013)
Agreed, especially with halving upon us - I fear the halving of profits of these large mining farms owned by asic manufacturers will try to be recouped by yet more ridiculous prices for mining gear, effectively killing the market & handing them the monopoly.