Different business models have different sales/profit ratios.

For example, a restaurant, you might have 25% of the gross for food, 30% for labor, 20 % for rent and utilities, and 5% for facility depreciation. Ends up 20% profit before taxes.

Now if you are doing roofing, you will be 25% material, 40% labor, 5% equipment, 10% insurance, and still at 20% profit...