....
example calculation with the assumption = BTC stays constant at 250GBP/BTC:
30k GBP = 3k MHs mine 13.05 BTC in 3 weeks = 1087.54 GBP
after 50% fee = 543.77 per week profit
after 3 years = 84828.12 GBP
Is this realistic?
After looking at it no it is not realistic to assume you will make the same profit every week for 3 years. You are not thinking about difficulty change. Also in 3 years most miner's are obsolete. I can't imagine a miner that will run profitable to 3 years.