Many grocery stores/supermarkets are typically squat affairs with a lot of allowance to expand vertically. That adds to construction costs but not to the land cost (which is the expensive part in a city). They could design supermarkets with growing space within a second storey. And because they're growing in trays or lightweight aggregate, it wouldn't have a metre-deep layer of damp dirt to account for.

(Obviously the construction costs could still outweigh the savings in transport and spoilage.)