In most cases, granite slab countertops should also be installed by a pro. Granite Countertop Costs. This is where granite slabs have a distinct advantage. As we noted, the installed price for slab granite countertops is $80-$150 per square foot. The granite tile installation costs can be as low as $50, though up to $75 is fairly common too. The material costs less because the tiles can be produced from smaller pieces of granite.