Back in mid nineties I was working at the auto dealer and I remember that we were charging $1200.00 to custom re-upholster the car with leather seats. Now that $1200 included a lot of manual labor to custom measure the seat and then manually stitch, take seats out, install the new covers - not just material. I would imagine that about 75% of the cost was labor. I don't see it being more than a couple of thou, as it involves the same amount of labor, so difference is only in the cost of leather vs. leatherette.
I wish that leather was an option, but it is what it is.