If I was after a service that I was paying for and someone came in to 'interview me' before quoting they'd be out the door in double quick time.
Its an arrogant approach to doing business IMO, going in with the attitude ' I might let you pay me a lot of money for the privilege of
having me clean for you'
I would rather leave them with the impression that it would be a privilege for us, to clean for them.
Your right though, face to face will produce more results.