Paying for attention is good. nostr:nprofile1qqszpreneylpzvlvhdzy4sp6mucdgg307a7jypn7a3t8860hfs8fp2gpz4mhxue69uhk2er9dchxummnw3ezumrpdejqzrthwden5te0dehhxtnvdakqv4lmha is working on a variation of this.
Biggest problem to overcome is spam/trust.
Otherwise I build a botnet of fake npubs to watch your ads and run you dry, with zero value to the advertiser. So that feature needs to built after every other part of Nostr IMO.