My work laptop (i5-560M) gets 0.8 chainsperday and uses 40 watts from the wall, it's faster than about 500 watts of my old rackmount servers (not to mention essentially silent and 1/100th the size).
You are right that it does not make sense without free electricity given current difficulty and price ~0.30$
I measured them with a Voltcratf energy logger at around 300W with both cpus and hyperthreading on, running H10
With the 'old' H10 they do around 0.3 cpd, with the version from github goes down to 0.22
So doing the math gives us
block/day = (1 - 0.86185294 ) * 0.22924828 = 0.031669976 which is around 1 block every 30 days
12 xpm * 0.30$ =3.6$/month
power consumption
330W = 7.92 Kw/h a day = 237.6 Kw/h per month
so to *break even* (no profit) you need an electricity price of less than 0.015 Kw/h (237.6/3.6) and without factoring in things like cooling,internet connection etc.
If on the other hand if you don't have to pay for any of the running costs with 10 machines and current prices you could get around 36$/month from some piece of junk equipment lol