Well,since mag-uyab na sila depende na sa sabot since they are in a relationship already.I know of some couples who have joint accounts so its really not an issue.
But, if it's a date between two people who are still getting to know each other...the guy should pay especially if he is the one who asked the girl...i said,especially because it can also be the other way around...like, if the girl asked the guy out then she should pay.