How much is he charging?

(That is a legitimate question to help us evaluate the validity of this "offer".) Whatever the cost, this "deal" bears every indicia of being fraudulent and untrustworthy.

This is not how the airlines operate. A common punishment is not only canceling tickets, but also banning participants in such schemes from future travel on the airline.

You would do well to read the Terms and Conditions (T & C) of the frequent flyer program whose status you would be "buying".