Every time you turn a light switch on or use an appliance, you are being charged for the electricity used to run it; this cost is extremely difficult to track, is different for every device you own, and adds up such that at the end of the month the cost is non-negligible (at least to the point where you probably are paying more on utilities every month than streaming media services)... and yet, while people, in the abstract, care somewhat about reducing their usage of such things like water and electricity (and thereby put in at least a bit of effort to prevent the most egregious of wasted costs), almost no one is crippled by the "mental load of evaluating whether each" time they flip a switch or turn on a faucet is "worth it". It is kind of ludicrous that this argument against micropayments somehow holds as much traction with people as it does when essentially all people experience not only experience the obvious counter-example so often as to be nearly every waking minute of every day, it makes up a significant fraction of their overall expenses.

I believe if the incremental cost is small, the mental load would mostly fade into the background, just as I am aware that there is a cost every time I turn on the lights or the faucet, but it doesn't have a large impact on my usage except that I remember to turn off the lights when I leave a room and don't leave the faucet running when I soap up the dishes.

I think you missed the intent of what I said: let people set their payment settings in any way they want to