It's worth bearing in mind that the insurance required to cover those for loss or damage would be fairly high.
For example, Paisleyfreight would charge an additional £35 for upto £1000 plus what ever the actual postage costs, so £99, providing they are fully insured, isn't exactly extortionate, plus ebay actually take a percentage of the postage you charge!
I've had people moan about postage in the past, but if anything goes wrong (damage or loss) where do they think the money to re pay them comes from!?
In regards to the price of the seats, it does seem a bit strong, maybe £1000 - £1,200 is a more sensible price for someone with large overheads, etc, but if someone is willing to pay that and they're happy with them, then that's what they're worth I suppose.