Comment by dalke

"A few percentage points"? $2 in profit/$18 in cost is over 10%. That's nothing like the ~1-2% grocery store profit margin which I think of when I hear "few."

Quoting one source: "Total pretax profit for the industry in 2009 was about $5.2 billion," and "Convenience stores’ gross revenue for 2009 was more than $505 billion." "While the average gross revenue per store for cigarettes was about $576,354, the gross profit on those sales was closer to $89,923. Cigarettes are the second highest-ranking profit producers for convenience stores, after nonalcoholic beverages, which provide each store with about 18 percent of its profits." "Motor fuel [...] provides a gross profit margin of only about 6.4 percent"

That puts detergent a bit under the 15% margin for cigarettes, but a lot higher than the margin for the store as a whole, and higher also than the margin on motor fuel.