Just let him pay for your coffee. Some guys are old fashioned like that. Pay it forward by taking one of your girlfriends out for coffee and paying.
Some women take a guy paying for some little thing like that as somehow crossing a boundary. I think that’s short-sighted. It doesn’t have to mean anything.
I make six figures, and I still let my father pay for dinner when we go out. I pay it forward by buying dinner for my friends.
This is also a good way to judge a guy’s character. If he starts acting like he’s entitled to certain things of you since he pays for your coffee, realize that he always had these expectations and you were just going to have to deal with it later rather than sooner. Best to know now so you don’t waste any time trying to be friends with an idiot.