The two I had done for the QAR cost me $600 at the local upholstery shop. IIRC the marine vinyl I went for was around $25/yard. They had to replace a little foam in mine, but not much.
Are you sewing your own covers?
I can sew pretty good, and I'm man enough to say that, but I'm not going to even try doing my own covers. I took them to an upholstery shop which is re-doing them for a reasonable price (for my area), so they should be done in a couple of weeks. I'll just flip the Starcraft seats I dyed a while ago, they just didn't get black enough for me, and wouldn't really look right in the van.
Before pic for posterity