If proof of work is the "payment" to prove that you're human, many AI startups will outbid poor people living third world countries. They will even outbid some Americans.

Yes, those AI startups can also buy cheap Android phones at scale, but it's a bit harder because they'll pay for stuff that their bots have no use for (a screen, a battery, a 5G radio, software, branding, distribution, customer support etc).