There is also the rather obvious and oft-overlooked fact that mining generates waste heat, and there are lots of people/places that actually need heat. Because mining hardware is small, portable and scalable, if you're already heating something with electrical resistance it may make sense to use mining ASICs instead and at that point you don't really care about the cost. You still need a full node or a pool to take part but I think that'll be easy to run even at high traffic levels.
Seriously Mike? People will use miners for heat? Man for a smart engineer you sure say some pretty stupid things.
...and before anyone jumps on hazek, keep in mind: heat pumps. Even if you are using electricity to generate heat because you have to - natural gas and oil are way cheaper in most places - if you have to pay a bunch of capital costs anyway to buy Bitcoin mining equipment, equally you can pay the capital costs to buy a heat pump instead and have
over %100 efficiency in turning electricity into heat. No this doesn't violate thermodynamics: the excess is taken from outside, leaving the outside colder that it originally was. Think a refrigerator run in reverse.
The point is, you can't just assume people "won't care about the cost" and mining will happen regardless of how low the return is, because you can use the cost to do something even cheaper, something that doesn't involve Bitcoin at all.