They were planning to go to a game for a couple months. Not explicitly but in the way that any two grown people doing something together likely would, they were each going to pay their own way. Once they settled on the game the friend said "cool, you can look for the tickets, right?" or something like that. But no discussion of either person ultimately paying for both tickets.

Then it got linked to the bday. Friend wanted to go big for the bday, did, and then figured bday guy would reciprocate by getting the tix (not stated either). He got upset about that, and when he later told the other dude (bday), the dude was hurt that he didn't just say something because there was kind of a weird distance/pause in a longstanding friendship.

Too much drama for me.