Just say "Thank you, I'm sorry we dont have more in common."

I had a blind date some years ago, and, she invited me to lunch. I picked up the tab. In the parking lot we were discussing the rules for dates these days, and I said "Generally, the rule today seems to be, equality. If I invite you to lunch, I pick up the check. If you invite me, you pick it up.." she remembered that she had invited me, but that I picked up the chck, she said "Well ! I dont have a penis!" I replied "Well, I do, but, I've never tried to pay the check with it!" Naturally, I never saw her again. No sense of humor at all. A fatal flaw to me.