I should clarify that 2 slabs would have been enough but it would require unfortunate piecing around the cooktop that we don't want. So the 13 sq ft out of the third slab isn't additional...its part of the original 60 sq ft they quoted. But now we are being charged for 73 square feet plus there is a fair amount of waste in the other slabs, one piece 50x54" that the fabricator will get to keep and resell as remnant...but we are paying for! Is this customary?
thanks for any input.

I have also been told this. We just purchased quartz for a master bathroom countertop and were required to buy a minimum square footage so we replaced the countertop in the other bathroom as well! Think about if you can use it any other place. If I purchased it, I would keep it, I would not let them have the rest of the slab, even if I had to sell it! Good luck, it does come out beautiful and never has to have anything done to it.

Thanks, nhoff634. I thought perhaps we were just being taken advantage of, its good to know this is typical though. Glad to hear your countertops turned out nice! We will take your advice and use the remnants ourselves.

@bbarick, this may not help you now if you have already decided on your purchase, but this type of dilemma is just another example of why concrete may be a material to consider. With concrete, the artisan will be able to custom design your pieces to spec, and mold to these designs without waste, which in turn may end up being more cost effective, while providing a beautiful one of a kind improvement to your home.