Mining being a free market, it should be the case that the supply (miners) expands and ajusts until the activity is about as profitable as any other business. In that case one would expect miners to make only 10-20% over costs.
(However, since the difficulty and price change rather quickly, the mining market may far from equilibrium, in either way.)
The set of miners and the set of people who believe in bitcoin-to-the-moon may overlap to some extent, but do not have to. A person can be skeptical of bitcoin but engage in large-scale mining (or day-trading) if he thinks that it is lucrative. Bythe same token, there seem to be many bitcoiners who day-trade altcoins even though they think that all altcoins will die.
The huge cost of a large-scale mining operation is not proof of long-term faith in bitcoin. The investors must know that all that equipment will be junk within a year anyway. They are betting that that BTC price & total hashrate wll be within certain ranges for the next year or so, so that mining will yield more (in dollar terms) than their investment, within that time frame. Otherwise they should have either kept their dollars or used them to buy bitcoins on the market, depending on their long-term outlook.
Good post.