From my brief research, the economics of Bitcoin mining with a Radeon HD 5970 seem a little too good to be true, especially if I buy a supercomputer for a friend in a college dorm with free electricity, or something.
Can anyone tell me how much bitcoin they are really generating per month with various setups, how much you are paying in electricity, as well as broad future on the future value of bitcoin?
That's 12kWh at let's say a $0.12/kWh residential electric rate ( http://www.bitcoinminer.com/post/2361900289/where-to-mine-el... ) that's about $1.44 per day for your electricity.
A 5970 hashes at just under 600 Mhash/s, per http://en.bitcoin.it/wiki/Mining_hardware_comparison so punch that 600000 number in as khps here: http://www.alloscomp.com/bitcoin/calculator.php
and it shows that at the current difficulty level, you should generate 50 BTC about every 3 days and 29 minutes.
So in a 24 hour period you get about 16.55 BTC per day. Converting that 16.55 BTC to USD: http://bitcoin.1t2l.net/widget/?from=BTC shows you earn about $15.28 per day with a rig holding a single 5970.
Then to send those BTCs to your PayPal, you use http://coincard.ndrix.com (starting again monday morning) and you lose 3% doing that conversion so you end up with $14.82 in revenue per day. Subtract the $1.44 in electricity that nets you $13.38 a day. If that were to hold, you'ld have the card paid off in well under two months.
That said, ... difficulty is rising (fast! ... http://bitcoin.sipa.be/speed.png ). If the BTC/USD exchange rises more ( it's had quite a run http://bitcoincharts.com/charts/mtgoxUSD#rg60ztgSzm1g10zm2g2... ), then that payout might continue at these levels. Otherwise, the payout from mining will decrease.