Having looked at the website, my only observation is that it isn't granite - it's tiny bits of granite pressed into a polymer material and set hard.
Strikes me that's a bit of a swiz - because the high cost of granite (or indeed other slab materials that are hewn from solid rock) is because of the cutting, processing and transforming cost.
However if you know that and have gone into it with your eyes open and compared at least 3 alternative quotes for similar things, including real granite (which should be ruddy sight more expensive) you've probably done OK.
I see it as buying chipboard, when one could buy real wood.