Sometimes I go to a fast food restaurant and discover that while I don't want fries, it's cheaper to buy the whole combo meal than it is to just buy a burger and drink a la carte. If I buy the combo and throw away the fries, nobody's going to argue that I've cheated Wendy's and owe them for the difference in price. But I'd agree they're still free to refuse me service in the future on grounds of wasting food.
I want a Big Mac, 2 cheeseburgers, a soft drink and fries. Using prices from https://www.fastfoodmenuprices.com/mcdonalds-prices/ , I have two options: a) Big Mac meal ($5.99) + 2 cheeseburgers ($2.00) = $7.99 or b) 2 cheeseburger meal ($4.89) + Big Mac ($3.99) = $8.88
If I order option a, McDonalds "loses" $0.89. Am I committing fraud?