I don’t order hamburgers but I’m sure many kids do. McDonalds and others have worked hard to maintain price stability in their “dollar menu” items whereas the upper tier stuff has shot upwards price wise. The feature sandwiches are between $5 and $6 in my market. The basement level menu items have shrunk in size and weight while price stays fairly stable.
I agree with your analysis.
If you compare to say White Castle, where the sliders are nearly a buck each now, McD has held the line on price pretty well on that first tier burger.