one data point - lemons - gristedes vs. gourmet garage
This didn't turn out as I expected.
pre-bagged "2 lb." bag of lemons at Gourmet garage, $4.99
no particular weight bag of lemons at Gristedes, $3.99
actual cost per pound:
Gourmet garage, 1 lb. 12 oz actual weight, $2.28 per lb.
Gristedes, 2 lb. 7 oz actual weight, $1.64 per lb.
Your mileage may vary. Next time I weigh in the store. My scale is not legal for commerce. The more expensive ones might possibly have thinner skins and produce more juice per pound, I doubt it.
Additional data point: Illy whole beans medium roast, labeled $15.39 in Gristedes.
Bought Illy whole beans medium roast labeled $14.99 at GG, scanned at $15.99, corrected when I spoke up.