Relays have no incentive to cooperate. You cannot pay "relays" collectively, you can only pay a specific relay. And other relays have no way to tell that the payment was real.
With proof-of-burn, you ...
That's also true of aut-ct (which is private proof of utxo ownership) and proof of work. But in any case I see nothing wrong with a user paying several relays, separately?
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