It can be pretty hard to calculate ahead like you have done as there is really no way of knowing how things are going to be.

You assume that BTC will hit 600 USD, but there is no certainty that it will or it will not.

I started my videos 28 days ago and so far my Genesis Mining 10 GH/s contract has paid out 21.3 % of my ROI.

Of course I didn't have to pay that huge wire fee charge like you had to.

If you had not paid that, you would have been much better off.

If the daily payouts would get to a point where they were making no money I actually think that a lot of miners would just stop mining as there would be no profit for them, so instead of the difficulty keep going up, it might actually level and could even go down.

Just my thoughts.