Sounds like it was actually a perfect question. It made it crystal clear that you and the company didn't see eye to eye on work conditions, and that neither of you would be happy working together.
Personally, if the expectation is to work 50 hours a week, then the question to ask them is "OK, do you pay 25% more than the average salary for this position?"
Of course, the only reason you'd ask such a question in the interview is that you have already decided you don't want the job. But the response can still be illuminating/entertaining. :)