It was kind of fun doing this math back when I was a freelancer. An hour saved would literally produce more money than the order cost. But really, it would have been better to save the money by making food ahead of time.
Well, if you value an hour of your sleep or entertainment less than $15 dollars (if, for instance, you like to cook), then sure, spend it on cooking instead. Many of people would rather not, and their revealed preferences show it pretty clearly.