We use Hard Balls Solvent based Fabric Protector, safe for all fabrics, better bonding to the entire fiber not just the edges, doesn't re-wet the carpet, accelerates drying time, no freeze issues like water based protectors, cost per square foot should be about 2.5 to 2.8 cents a square foot. We charge .15 cents a square foot. I haven't found a better protector in IMO, and we have tested many. We sell it for $45.00 a gallon.