He pays for you: You feel uncomfortable because you know he feels owed sex. His goal is to get something ie. sex.

You pay for yourself: Because you don't want to feel obligated to have sex. Your goal is to avoid something, coerced sex.

Can you see the inequality here? Him: risk/reward - You: risk avoidance

He still wants sex, you are paying for your own protection. How is this a date?

The handbook goes into why we don't do 50/50 in much greater detail. Read it.