Obie said:

Trader Joe's(small chain in California) has literally half the markup of
Vons/Safeway and yet is planning on expanding 100 stores in the next three years.

Even with the current pay, the companies are still making money hand over fist.

They don't pay union wages, do they. And they only sell packaged
goods, which require less labor to display. No meat to cut, no produce
to uncrate and place in neat piles.

A more apt comparison is a bookstore.