I actually really like your mention of a charity. Imagine trying to get the attention of someone like Bono. You likely couldn't pay *him* $20k for his attention, but if you donated $20k to a charity that he was advocating for, you likely could get his attention.
All that to say the proof of work isn't arbitrary. It needs to have value behind it. I don't want someone to feel like they need to jump on one foot while they ring my doorbell, there are ways where one's commitment to the attention will get the job done. But that requires more pretext.
I actually really like your mention of a charity. Imagine trying to get the attention of someone like Bono. You likely couldn't pay *him* $20k for his attention, but if you donated $20k to a charity that he was advocating for, you likely could get his attention.
All that to say the proof of work isn't arbitrary. It needs to have value behind it. I don't want someone to feel like they need to jump on one foot while they ring my doorbell, there are ways where one's commitment to the attention will get the job done. But that requires more pretext.