Network hashes per hour (currently 558 per second) = 2,008,800
Probability of mining 1 block (80 coins) in 1 hour (network/personal hashes per hour) = 1:2603
The network mined 20 blocks (1520 coins) within the last 60 minutes.
With your figures You should generate 0.58 coins per hour at a cost of 0.407 USD/coin.