That's so annoying, frustrating, unprofessional and unfortunate. I'd personally want to stop what I was doing, get dressed, let him know that I was leaving because he was showing little to no interest and that I was only going to pay him $X for his time. But then you risk a possible confrontation which no one wants. It's a tough situation to be in. Sucks having to pay full price when I'm sure you weren't even into it at that point. You probably just wanted to get off and go and have it all over with.
I probably would have done exactly what you did.