Not surprising since the cost of the new Jardines system he has fitted instead is only 531 ukp i.e one third of what he's asking for a used OEM system.
"but p&p will have to be payed by the returnee." That would be him (the seller) then. Very generous of him!
Wouldn't surprise me at all. Not after having been quoted over 1100 euros for a new alternator for a Ténéré. I remember when I had my GT750, now in Sweller's possession, that a complete exhaust system was over £1100, and that was 10 years ago.