None of that answers the question of why a box of cereal that costs a dollar or so to deliver landed to a store costs me $8 to buy. Middle men are taking a huge chunk of the pie!
Delivery optimization, logistics, and last mile operations are an unfathomably difficult problem(s) to solve, so much so that the entire world participates and there are still enormous gaps in efficiency, many that likely will never be solved due to physics.
I know you're plain wrong about it costing "a dollar" to deliver. Even if it did, you do not pay for just the operational cost, you pay for the convenience, expertise, reliability, or many other factors that comes with procuring a contract/agreement.
If you have something to prove, then you're welcome to show the world how its done. Doubt me all you want, but you can't doubt the rest of the world.
> It costs pennies to produce, maybe a dollar in landed cost
Kellanova last had gross, operating, and net margins of ~35%, ~13%, and ~8%, respectively [1]. Likewise, Walmart achieved ~25%, ~4%, ~3% [2]. This isn't really compatible with "someone makes 700% of net profits on this box of cereal", unless you assume cereal is single-handedly subsidizing huge loss leaders for both its producer and retailers.
1. https://www.macrotrends.net/stocks/charts/K/kellanova/profit...
2. https://www.macrotrends.net/stocks/charts/WMT/walmart/profit...