This is a promo video for a firm that manufactures Corvette seats, but if you skip the first 30 seconds you'll get a look at what goes into one; they're essentially really complicated upholstery jobs combining CNC cutters and actual human beings with sewing machines. I found the bit about how they map out flaws in the hides, then cut around them, interesting (if wasteful-looking). And these guys even make their own foam.