Money is great at thwarting spam/Sybil attacks. You don't have to raise the price very much to make them fail.
Honestly I think "this person is real" is the wrong goal. You'll never accomplish it without a centralized state or some biometric monstrosity like that thing Sam Altman created.
Just settle for stopping spam.
Yeah, I think "pay to enter" or maybe "pay to be able to post" is ultimately going to be the solution. Then we'll have the paid "gated" social networks, filled with mostly humans, and the free ones will all be bot-swarmed wastelands.