[gumby]

So why is the store brand not in the prime spot rather than the bottom shelf. Is the major brand paying for placement?

[anomaloustho]

Yes, it’s called a slotting fee.

https://en.m.wikipedia.org/wiki/Slotting_fee

[gumby]

Clasic economics would say therefore the lower profit margin + slotting fee should equal the higher margin of the house brands.

I wonder if that's roughly true? I could imagine both yes and no. Classic economics, sort of by definition, can't take real world edge effects into account.