Just quote from S5 Thread
you can search in aliexpress for new unit in around $450
you can search in aliexpress for new unit in around $450
Just unboxed a couple S5's I bought a while back and found one of them had obviously been used excessively. It has soot all over the heatsink. I have submitted a WTF email to Bitmain...I guess they really are going downhill 
Bet you it still works great for a couple years.. My S1 has been running full steam for 1.5 years now.
Why is it still running you might ask? I like burning money.