I've gotten them from time to time. Once I tried to argue with the sender to see if there was a way to get him to buy without an appraisal. No... He was incredibly persistent though.
I've got this two times for two different domains. The sender didn't even bother to look at the recipient's address while using the same template for the email body. Try searching for the exact wording he wrote on google. You'll find many links.
(BTW, one of them was $30k proposal, while I never thought the domain to be more than $800 worth )