The price gap is real and so is the reason
A kit is $200-$600 for a two-car garage against $4,000-$6,000 professionally installed. That gap is not margin. It is film thickness, surface preparation, and roughly $30,000 of grinding and dust-extraction equipment that the kit assumes you do not have.
The acid etch is the fatal part
Every kit includes an etch packet because acid is cheap and grinders are not. Etching gives an inconsistent profile, cannot remove contamination or old coatings, cannot flatten anything, and leaves salts if the rinse is imperfect. The coating bonds to a closed surface rather than the slab.
When DIY genuinely makes sense
Two cases. A concrete sealer or lithium densifier. No film, hard to get wrong, and it stops a slab dusting for around a dollar per square foot in materials. And a purely cosmetic short-term fix on a floor you are about to sell or a shed you do not care about. Both are legitimate and we will say so.
The cost of getting it wrong
Grinding through a partially bonded failed film is slower and harder on tooling than grinding bare concrete, so removal adds $500-$1,500 on a two-car garage. The $400 experiment ends up costing more than the professional floor would have in the first place.
Want this answered for your slab?
Free site visit with a moisture reading, then a written fixed price. Across the BC Interior.