That is a complete joke. You put 2 5970 cards in a computer. That is a 1.3 Gh/s system. The electricity to run that at $0.10 per kw-hr (600W x 24 x 30 x .1) = $43.20 per month electricity. You will be generating presently 11 BTC every day. You will pay the electricity off in 2 days!
It is a great time to upgrade to a new computer system, if your computer is less than 2 gz, why not upgrade to a new computer and have an income of $15 a day that is far more than the payments.
make that € 0.20 ($0.3) / kWh where I live and maybe a lot more when we power off our nuclear plants... well, I see mining rigs shipped to other parts of the world.
Your point is still valid, even at $0.30/kWh.