Is it some kind of unwritten rule that he ALWAYS pay?

A
This afternoon my boyfriend and I went to Subway. He's usually the one to pay for stuff when we're together, but when I turned around he wasn't there, so I went ahead and paid for our food. Just as I took my card back, he appeared out of nowhere and asked why I did that & while he didn't look upset that I paid for the food, I could tell he was genuinely annoyed. He's always telling me not to spend my money when we're together but dude it's just a sandwich. Simmer down. Is anybody else's man like this too?