He should have been willing to pay for both of you because he's the one who asked YOU out. Period.

This concept should apply across-the-board, regardless of people's genitalia. It should apply whether the invitation is strictly platonic or if there are any potential romantic vibes that could hypothetically be explored.

If I ask another guy out on a date (I'm gay), I'll pay. If he's the one who asked me out, I'll let him pay for both of us if he prefers to...but I still go into it, initially, prepared to pay for my own share.

If I invite a friend of any sex or gender out to lunch or dinner, I'll likewise go into it prepared to foot the entire bill since I'm the one who invited. Although, in my experience, for most platonic meals/activities, everybody usually prefers to pay for their own share.

If you go into courtship armed with a psychological calculator, then good luck actually finding (or maintaining) that healthy life partnership.