As an aside, HD and Lowes do not have the machinery necessary to cut their own slabs so they contract it out locally
I'd say that the price you git is the average price, even from specialty suppliers. You'll be able to get significant price breaks from larger suppliers if you buy their leftover slabs, that's if you do not require too much sq footage. Most places will also have 'slab sales' at least once per year. Doing so I was able to get the price down to $30sq ft for the 4 bathrroms I did in my own house, rather than the normal $65-90 here. I also found that HD sells only the cheaper slabs. Many of the nicer patterns cost signifcantly more, and are only available from suppliers.