I think the deal they were trying to work is, "give us the speakers, and we'll agree to your price on the house." So the only way that would make sense is if he could get them to agree to a price at least $3500 higher with the speakers than without.

That's not including commission, taxes, fees, etc. So it realistically would be $5000 or more he'd end up paying for a new set of speakers.

Pioneer PDP-5020FD, Marantz SR6011
Axiom M5HP, VP160HP, QS8
Sony PS4, surround backs