Call em' out on it. I've said "I hear that several times a week and it's folks just to nice to say no." Challenge them a bit further but it's probably over.
Wrong timeing to challenge a potential customer. I'll do it when they think I can't help them, not when I'm working on closing. You want people to think you are trying to help them, not pissing them off. If it doesn't close you don't want to have them telling everyone what an ass you are.