The donut place is doing it wrong. They need to build the added 15 cents into the price of a dozen donuts. Since donuts are generally less expensive if bought as a group of 12, just add it in and everyone wins. Of course there will always be someone who gets a dozen donuts and then asks, how much is it without the box? (Same price, and we keep the $.15 as a tip.)
The donut place is doing it wrong. They need to build the added 15 cents into the price of a dozen donuts. Since donuts are generally less expensive if bought as a group of 12, just add it in and everyone wins. Of course there will always be someone who gets a dozen donuts and then asks, how much is it without the box? (Same price, and we keep the $.15 as a tip.)