Economics says that mining should be profitable... So why is it unprofitable?

[Robert Paulson]

That's kinda like asking why is Tesla's stock worth anything (https://finance.yahoo.com/echarts?s=TSLA), the company never earned a single dollar since it was created.
money today is cheap, interest rates are at 0, and people are speculating that bitcoin will go up in price and their currently barely profitable mining operation will turn very profitable in the future.

[Minerjoe]

As everything else, it s competition, the healthy base of any capitalistic economy.

You produce something or mine something until price equals marginal cost.
If it goes lower then that, you must stop cause you are losing money. There are large farms who can actually achieve this high level of efficient and mine at position where P=MC.
All of us, small miners are less efficient and we cannot do it anymore. This is no different then any other similar economy. More competitive and more efficient firm push out the rest out of the market.

So it s not the mining is unprofitable, only it s unprofitable for you and me. It s profitable for somebody else.