Do we all agree that this rig at 3Gh/s would net about 55 Bitcoins in a year at a 2% difficulty per month increase?...according to the calculator I used.

So, an approx. $2500 investment would bring back about $7500 in a year at $136 price of Bitcoin at the time of this post?

Is this how the math should work?

A true Newbie question.....