Re: Flaw in the argument
4-6 times? How much do Tesco charge for oil? Your maths stinks, and you're comparing oven chips to either from-raw deep fried chips or oven-baked jacket potatoes. You can bake chipped potatoes in the oven using a lot less oil.
And if your time is so valuable and you are so crap at peeling potatoes (half an hour? does that include stopping for a rest?) then DON'T PEEL THEM.