Quote from: BitLex on May 20, 2011, 10:15:52 AM

to answer the initial question: yes, it is.

let's say you only get 2x5850 (not 5870s) for $800,
2 5850s get around 700MHash/s and the rig will need ~375W (probably less, but let's just be sure),
at (very expensive) $0.3 per kW/h you'll pay $2.7 per day
at current difficulty the expected average output is 2.88BTC per day,
at current market rates (of roughly $6.5) that's $18.72 per day.

$18.72 - $2.7 == $16.02 per day
16 / 800 == 2% ROI per day

show me an investment opportunity that pays you 2% per day and i'll join it.

Actually, I did calculations too and:
Today Im earning 23$ per day (after paying bills) then +35% difficulty
In 10 days - 16,1 $ then +30% difficulty
In 20 days - 11,5 $ then +25% difficulty
In 30 days - 8,3 $
After 40 days ~600$
After 60 days ~713$ (few more difficulty rises)
I just assume that price wont change and Im good in predicting difficulty rise.

To get 23$ per day with current difficulty you need to have around 3.8 BTC per day, which gives 920Mhash/s (3x 5850)

If the price stays at 6.8$ most prolly u wont get back your cash, so your investment is risky.