Well my 4 S3s that I received on 8/14 have earned 0.9BTC in 26 days - they should hit 1BTC before the next difficulty. Initial cost was 2.64BTC. At the current rate of increase I break even in 4 months because I have free power.
Had I not had free power or very cheap power I doubt the units will ROI.
I got some batch 1 s-3's 2 for 1.35 btc mined them since july 26.
they have earned just over 1.1 btc and they power was .06 so they have 1.04 btc earned after power.
so they are .31btc in the hole. after 50 days I think in 25 days they will be even so 75 days to break even.
but I had the psu so that = 0 cost.
I was running the internet 24/7 anyway = 0 cost
and these have .025-.03 cents a k watt for power.