French fries/chips/whatever you want to call them. McDonalds buys its potatoes at around 20 cents to the pound. You can get about four medium fries ($1.79) out of a pound of potatoes. Even if transport, labor, and other overhead triples the cost that's still a profit margin well over 1000%.
Margins on soda are even higher while burgers and other items have more ingredients and complexity and are thus more expensive to produce.
Well, that is $1.50 profit. (Per medium fries) Sure it is alot compared to 20 cents. But let's not forget that, even though that is a big profit. You would need to sell a shit ton of fries to even make it worth it.
Sure McDonalds has enough money to buy potatoes at $1 by the pound, but that would mean they had to sell 80% (correct my math if im wrong) more.
With that said, it is still cheap for us consumers to buy it from them, than it would be for us to make it at home.
Just throwing my 2 cents in.
Also, potatoes don't just turn into fries. Someone needs to process them somehow, whether that's cutting by hand or just tipping them into a fancy fry-cutting machine. Someone needs to fry them. Someone needs to bag them and give them to customers. This whole post is people forgetting that raw goods require people to turn them into products. And in a roundabout way this kind of thinking, that fries shouldn't cost $2 because a potato costs 20 cents, helps support paying the workers shit wages.