Well first, if you can get granite slab for $40 a square foot, then buy it.
It starts at $50 here.
You can save some money by installing granite tile.
Remove existing formica. Install 3/4" plywood. Install 1/4" DensShield water-resistant backerboard over a bed of troweled thinset and screw to manufacturers specifications. Then tile.
Cupan Custom Tile and Paint