There are also other machines becoming caught in the updraft of appreciating values. I have a 1975 Ducati 750 Sport , 1 previous owner and in utterly mint original condition when I bought it for £5000 in 1989. That was the top price for this machine then , but I'd always wanted one , unusually had the money and it was the best I'd ever seen apart from when they were new.
Losing money on it was never going to happen given the demand for older Ducati's but I was amazed recently when I noticed that a restored example which had been 'over done' was sold for £18,000 !!! Only wish I'd bought the 750 SS which the seller also had for sale but couldn't afford without a loan which I have an aversion to !! The 750SS would now easily be worth £35-40,000 !!
Appreciating values in the collector vehicle market is a fact of life and although it is unlikely that many of the children and grand children of current Vincent owners will have the means to buy their own when they are old enough to ride one , the market will never be sympathetic to that issue.
The same situation has occured throughout the history of the motor vehicle , many marques have their Zenith then fade into obscurity for a while , sought only by the fringe fraternity only to be be ressurected by virtue of their historic significance then to be craved by a new generation of cogniscenti. The result of which is rapidly rising value due to the law of supply and demand.
Look at Bugatti , Alfa Romeo , older Ferraris , etc , etc . A ferrari 250 GTO was once an obsolete race car that could not be given away , now you would need £10M plus to prise one from it's owners hands. Even more surprising is the value of some quite mundane machinery , eg: a Ford Capri RS 3.1 went on ebay recently for £27,000 !!! MkI and II Escorts , albeit the warm variety versions, can fetch £35,000 !!!
As modern vehicles become more and more inane and the new generation of enthusiast discovers the qualities and history of the motoring past , historic vehicles will almost rocket in value , changing that is impossible.