They are a bit hard to calculate with. I know my hash rate will be 2184 for LC Difficulty I kept as standard import no clue what Pool Fee is.
The mining pools charge a fee to run the servers and take some of the risk. It's usually 2%.
At that point I will be making $420 a month with a elec bill of $75 so 320 a month Seems quite good. That is with 3 x 7970's with 5k should I get 2 rigs both with 3 x 7970's. So many things to think about.
But that's at the current difficulty. It is going to go up. It's was at 200 only two weeks ago. Make sure you factor in the decreasing returns.