Are we assuming the cost to build a restaurant in Midtown Manhattan, get ingredients delivered there, and hire workers to make the sandwiches is going to be the same as rural Buffalo?
It's a bizarre assumption to make.
That argument flawed because the higher foot traffic and sales rate are also material. You can have lower cost but also lower traffic. The whole idea of purchasing an awful burger from a franchise is price predictability and safety.
Locations don't all have the same rent or minimum/prevailing wage. Not saying there isn't funny business but we shouldn't expect prices to be the same for locations with different costs.
Locations also don't have the same amount of sales.