Don't trust calculators. You're missing one huge piece of variable: difficulty. Do you think the difficulty's going to stay like that all year?
You are correct, the difficulty will change..... but the value of btc will change as well. What if it goes really high this year?
That's the other variable that you gotta consider when mining. If BTC goes way up...mining equipment is golden.
The real question if you are thinking about mining is, why are you doing it?
If you are mining simply for profit, then you might be wasting your time.
Real miners mine not only for profit, but to support the bitcoin network.
I'm just sayin, do your homework before you purchase a miner if you wish to be profitable.
You may find out that it's not worth your time, or out of affordable reach.
BTC and mining is a movement for change in world finance, not just a profit venture.