Miners could make a profit at $1/coin. The issue is that profit comes from somewhere. And that somewhere is new money being put into BTC. Hence, BTC is negative cashflow.
The value provided by a database such as BTC is that it provides a record of 'who owns what at what point of time in history'. I can argue separately about why the 'immutability' of this database itself is a value created by Bitcoin, for which holders can be willing to pay premium for.
Miners earn profit if Operating Costs > $ value of (Transaction Fees + BTC mined). Over a long enough timeline, Fees + BTC mined will ~~ operating costs of the rig. If not, more miners will continue to see economic opportunity, and keep joining the miner pool till that equation is balanced.
The other source of BTC value going up need not be more demand for it, let's say over next 12 months. The ~6% inflation could show up there too.
What am I missing?
We can estimate 300k transactions per day, which implies about $150 revenue per transaction. Miner revenue is your cost: it is what they extract from the Bitcoin system.
One Bitcoin transaction costs on the order of $150. It's really expensive.