None of that matters. You simply do the math for when your miners will stop being profitable (when you'd stop mining), and instead buy btc and hold until that time. You will always end up more profitable that way than if you buy hardware to mine.
I didn't do this the first time and instead bought miners from KnC. I will now be lucky if I make half as much btc as I could have if I just bought it at the time I placed my order. The only true winners in the mining game are those who make the miners. The rest are just chumps regardless of how you try and spin it.
In the simple situation you and many others keep repeating, yes. But there is a whole other side of cost-basis, time-value-of-money etc that I won't bother to bring up. If you understand you understand, if you don't then that is why Wall Street & FED never has to worry about the masses rising up against them
When it comes to taxes and being a legit business, I agree. However, I and most I assume, are not in that situation and can easily forgo those complications. For us, it does not make sense to pay another company to produce an item that will "mine" back less than it cost us to purchase in the first place regardless of the fiat equivalent of our investments or payouts.
For an individual...for any given profitable timeframe, if the product will not produce more btc than it cost to purchase initially, then it is not a good investment.