There's a sentiment here that I think is valid and I'm struggling to tease out the best version of it, along with providing a valid response.

I'll mention that, in an extreme case, one could provide a proof-of-work challenge that's directly tied to some cryptocurrency mining effort, so that the work/energy expenditure is captured by the one providing the challenge. This has the effect of the challenger giving money to the one providing the challenge, just in a real-time proof-of-work way. Since money is effectively being exchanged anyway, this punishes systems that don't allow up-front payments to do away with the page load delay.