Looking at the Kroger 2024 Annual report shows that they have 22.3% gross margin . they pay dividends, had a stock buy back, etc so its entirely possible that they had a very low margin but gross margin seems to be similar to a home builder.
Sales $ 147,123
Merchandise costs $113,720
Rent, Depreciation, Amortization $655
Gross profit $32,748
for a gross margin of 32.7/147 = 22%