Among the many things you have to put up with if you don't cook for yourself. (I have a pretty big appetite, so I have the opposite problem; I find that restaurant helpings leave me still hungry).

Still, I understand that some people live in conditions that make cooking for themselves hard (packed work schedule, inadequate kitchen facilities, etc). You should consider making a comment to the staff at the bakery that they sell different sizes of muffins, maybe the small ones for 15 cents less so they still make a higher profit margin. They wouldn't necessarily have to buy different muffin tins, just fill them with less dough, since bakery muffins are often all top anyway.