The worst of these I ever did was try to prove to someone that it was cheaper per cheeseburger to make them himself than it was to go to Wendy’s. His argument was that he couldn’t buy a single slice of tomato, cheese, lettuce, a single beef patty, a single bun, etc. But this is what he had for lunch everyday so I was trying to explain to him that it would be cheaper per burger to just buy all the ingredients and make them himself. I went to a grocery store, priced everything out to buy in the smallest amounts I could, and then did the math on how much each burger would cost him that way. It was drastically less. He then moved the goal posts to “but then I’d have to cook it and that takes time” so I addressed that argument with “driving to Wendy’s and waiting for them to make it takes time too and now you have to factor in the cost of gas you’re consuming during that drive into the cost of the burger so now it’s even more”. He stopped replying to the thread so I took that as a win.