I was valuing it at about £5-7K based on the following:
Original price (probably £1K by today's value, thus assuming this is a "new" machine).
Rarity only 200 made according to one source (£2-3K based on min x2 sale value).
The fact it is a working prototype that is importantly unique in being the last of big C (£2-3K).
But how can you actually judge it's worth... if I had it I'd have it boxed away and would only sell for 20-30K, which I'd never get as most people would have a similar valuation as above.
They change hands for 1/3 of that price in working condition so it's typical ebay loser going OTT with his mouldy old shit
