McD’s has doubled prices with rising profits
[1] https://www.mcdonalds.com/us/en-us/full-menu/5-dollar-meals....
*Prices and participation may vary.
That said, McDonalds corporate isn't running promotions unilaterally. Instead, promotions are proposed by committees elected by franchisees and voted on by franchisees themselves, so participation rates tend to be high.
Delivery and final assembly of food is not McDonald’s’ business.
I haven't eaten McDonald's in a while, but from what I remember the food arrived fully assembled.
The franchisors’ profits and profit margins are nowhere near McDonalds’.