Did concrete go up that much with the fuel prices or what. I was quoted $4sqft to pour a 27x40 shop floor 4 inches with fiber. I was quoted low to mid 3's last fall. Seems like a big increase.
i work for a concrete company and for 3500psi and fiber your loking at around $105 a yard in maryland
I would go 6 inch depth too if there will be vehicles/machinery on it.