I've never seen a prep time that came close to how long it takes me. Usually at least one and a half to two times as long.

I don't think, though, that prep time is meant to include baking time. It's supposed to be the time to mix ingredients and get the pan into the oven.

Prep time doesn't include realizing your sugar jar is almost empty so you need to empty another bag of sugar into it, or rummaging through your spice cupboard and the overflow spice cupboard for the strange spice you haven't used in a recipe in four years, or replacing a fuse after running your hand mixer and microwave at the same time blows it out.