Charge the maximum the market will bear.
Why is your stone so cheap and concrete so expensive? At the prices quoted, he would make $134 an hour. That on top of $400 already charged for labor, which I assume is for 1 more finisher and a laborer. Three people and 6 yards makes for an easy day. No overhead was mentioned so I doubt if there is much. Great if you can get it. If he added $400 for his labor plus a 20% markup, it only comes out to slightly less than $1900. About $4.20 a square.in northwest oklahoma,i pay 5 bucks a sq ft for material and labor on flat slab work.