The Gold Star ad nicely illustrates why it is always up to buyers to vet the purchase of any old motorcycle for themselves despite what the seller might have told them, and whether or not some sort of legal remedy might be available to them later. In the case of the TT being discussed on the Triumph Forum the possible inaccurate representation by the seller actually is fairly subtle. TTs do sell for more than standard Bonnevilles, so it's a question of how much, if any, "additionally-inflated" the value might be if a TT is represented by a seller to be 1 in X rather than 1 in Y.
While the issue with the TT's value might be subtle, the G.S. ad should make the buyer's own responsibility in a transaction completely obvious. If a buyer took at face value the first line of the ad "A brand new old stock Motorcycle in mint condition,"
and spent £21,995 based on the seller's assertion, it would be difficult for me to muster any sympathy whatever for a later complaint that the seller had misrepresented it. Even if the seller hadn't mentioned the new clutch, valves, and rings.
Because of this, it falls almost entirely on the buyer to figure out how much an old bike is worth to them irrespective of how it is represented by a seller. This is the case even if after spending lots of time and money in some legal proceeding they might be able to convince a judge to award them some X vs. Y difference in price. It's probably worth mentioning another "problem": even if a seller thinks
a particular bike is worth £20,000 and a buyer knows
it's only worth £15,000, they're just not going home with that motorcycle even if they are willing to pay £16,000.
Further, misrepresentation of an "intangible" like rarity is quite aside from tangible, quite relevant issues when buying an old motorcycle, such as if it has the correct carb(s), the electrical system has been changed, there's a heavily worn cam, the valve guides are worn, the rings are seized by sludge, there are missing teeth on some of the gears, etc., etc. Unfortunately, often the only way to learn the answer to some of the questions about mechanical condition is after a machine is in your own garage. Despite anything a seller tells you, and your own careful inspection, it would be foolish not to mentally factor in some additional cost to repair broken/worn parts.
Luckily, most internal issues can be fixed later if necessary without having to spend a fortune. What can't be fixed is if the 'Gold Star' you just bought has a B33 engine in a "reworked" A10 frame, DBD engine in a BB frame, 'Std' gearbox restamped 'RRT2', front wheel from an A65, etc. This is why it is foolish for a potential buyer of any old motorcycle, let alone a rare or "highly desirable" one, not to be armed with all relevant information that is available when inspecting it. When buying old motorcycles it's "trust, but verify," with a very strong emphasis on the "verify."
p.s. Seller beware
. It's easy to forget the other side of the coin. While most people reading this probably know what their Gold Stars (and Triumph TTs, and Brough Superior SS100s, and...) are worth, that doesn't mean their spouses do. At some point when your future-widow becomes a seller you can be sure a potential buyer will try to convince her the useless old bike is worth only $2000. If she does sell it for $2000 it's entirely your fault
for not having informed her. You selfishly squandered $20,000 (or whatever, in 2014 dollars) of joint family money for something entirely for your own pleasure, and because you failed to provide her with relevant information she won't even see that money after you're dead and she is forced to apply for Food Stamps. Live with that guilt as you're turning over in your grave...