cost of a btc has nothing to do with cost to mine it. mining difficulty will naturally seek an equilibrium based on worth of btc. worth of btc is determined by demand for them (increase of supply is set up to remain known) - nothing more, nothing less. not sure why this fallacy is repeated over and over again on these boards.
Not a fallacy. That's why.
Whilst the cost to mine a bitcoin is less than the price to sell one, there will be an incentive for people to start mining. Difficulty and even technological advances are irrelevant.
It's not only true of bitcoin, it's true of gold and very other natural scarce resource that I've looked at so far. Not precisely but certainly the same order of magnitude.
Price of a fish ~= Cost to get that fish on your diner table.