We could start a company calculating realistic citation-price exchange rates :)

I'd also say that a citation in a top journal is worth more than in, say, a book chapter

It was an Iran-based research group so you wouldn't be able to receive their payments without immediately being tracked by the intelligence services, I'm afraid :D

I didn't ask whether they were open to negotiating prices :)

Interesting article, thanks for sharing! I haven't reported them, mostly because I think it's just very sad that academia incentivizes people to make such desperate attempts. But I understand others would.