With micropayments, the server owner makes 1 million requests times 0.05 cents = ~$500

The status quo with those js PoW pages doesn't really benefit the server owner at all, it's wasted energy.

I mean proof of work is always wasted energy, but I figure it's better to kill two birds with one stone.

CoinHive was one example of this. (I think this is a correct link? https://github.com/cazala/coin-hive). Although I think ideally you would want to have some sort of browser plugin or app that runs on bare metal instead of a proof-of-work in the browser, because RandomX is designed such that it's slow when implemented in JS (https://github.com/tevador/RandomX/blob/master/doc/design.md)