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Charge for the grind, not the brochure. A two-car slab is usually about 400 square feet. Full-broadcast flake with a topcoat is not the same job as a solid-color 2-coat, and neither is a job if you only etch the concrete.
The number that sinks underpriced bids is prep. Diamond grinding a 400 sq ft floor at a realistic 80 sq ft per hour is five hours before anyone opens a kit. Coats then run on the billable area — the slab plus waste — because roller loss and cut-in eat material the brochure coverage ignores. Full-broadcast flake is typically 0.15–0.25 lb per square foot; contractors who “guess a couple of bags” buy more on the way back.
Then add cracks and pits as extra hours and extra fill, add the drive as loaded labor plus vehicle miles, mark up overhead on that direct cost, and take margin as a share of the price you send. A $4/sq ft special on a two-car flake grind is often below walk-away before the first bag of flake.
Open the calculator with a default 20×20 full-flake grind. Switch prep to degrease-only or type $1,600 as the price you are considering to see the cheap special fail in the numbers.
Price the grind, the coats with waste, the flake you actually broadcast, crack and pit patch, travel, overhead, and the margin you intend to keep. A flat dollars-per-square-foot special that skips mechanical prep is how a two-car job comes back as a peel.
They usually assume degrease-only prep and ignore travel, flake bags, and payroll burden. Full diamond grind on a 400 sq ft slab is often as many hours as the coats.