As mentioned above I think someone added a zero to the true estimate.
Having had a discontinued PO 2500 valued for insurance purposes by an Omega boutique also run by Watches of Switzerland (who own Mappin and Webb) I think they will have put “RRP for equivalent current model” on the valuation. The seller either doesn’t understand or is being misleading on that being a valuation for the current watch.
Still even £1000 seems a lot, what would the scrap value of gold run to in that piece?