Either my pictures aren't very good or the wisdom of the crowd isn't what I thought. The company agreed with me they are cutting a slab for the back wall that will run vertically like the other two slabs and placing it over the slab already installed on the wall. They are then cutting a one inch strip of marble and finishing it to cover the seam. They were very gracious and admitted the back wall was a mistake on their part.

m a fabricator. If your fabricator is buying stone specifically for your job (not from his inventory) then his price will reflect the waste which you are paying for. Customers often think this is unfair but If the fabricator did not include the cost for your material in the price he would have a business that collects remnants instead of one that makes a profit. My shop has over 2000 remnants and we scrap half a dozen dumpsters of remnants every year. If you have a particularly beautiful stone that is highly desirable (meaning he can expect to sell it as a remnant quickly) then he might be willing to give you a credit. We do not let customers "hold" their remnants indefinitely as that requires us to assume responsibility for the stone with no certain prospect it'll every actually be used. We have on occasion delivered the remnants to a customer for storage at their site but most don't want that.

Your fabricator has made a mistake alright; he failed to properly set customer expectations. Those seams are excellent. You want nearly invisible, get Corian. Run a black Sharpie down the seam and rub it with your finger please, then forget about these seams please.

They are fine. Run a color matched Sharpie down them and they'll nearly disappear.