Plus it's not just about total time between "I want food" and "Nom nom". There's also the matter of how usable that time is. On a good day it might only take me a few minutes longer to get fast food, but all of that time is spent behind the wheel and most of it is spent driving. Making a sandwich at home, on the other hand, only about a minute is spent actively handling food. The other seventeen minutes while the patty cooks are free; I can it spend doing anything I please. So instead of comparing twenty minutes for fast food vs. eighteen minutes for DIY, it's really more like twenty minutes vs. one minute.