[lotsofpulp]

>I can't imagine it coming down to a store having higher costs alone.

Your other option is assuming there is industry wide financial reporting fraud across multiple businesses and multiple countries for many decades.

Stores have different costs due to selling:

1) different quality of goods

2) employing different quality/quantity of workers

3) different locations having different real estate/insurance/tax/labor costs

4) offering fewer or more services/products

Etc.