Whole Foods announced earlier this month that its stores generated an average of $983 in annual sales per square foot (PSF) in 2013. According to statistics published by the Food Marketing Institute, the average sales PSF for supermarkets in the United States is $360 (based on a median total store size of 46,000 and median weekly sales per supermarket of $318,170).
In the Greater Philadelphia Market, the high-volume Giant Food and ShopRite stores are most likely generating north of $500 PSF, and perhaps even close to $800 PSF in some cases (a 55,000 SF store with $44 million in annual sales, for example).
For those immediately wondering about Wegmans, they certainly have incredible sales numbers, but with stores so large (132,000 SF in Collegeville), reaching Whole Foods-like PSF totals is nearly impossible. My guess for a store like Collegeville is about $600 PSF ($80 million in sales).