Hi,
As has wisely been stated before, a vintage item is worth whatever someone is willing to pay for it.
For example, although i have heard good things about the Kirby models 1HC/Heritage and 1HD/Heritage 84 I do not care to own one--or at least to pay much for one as I am not a huge Kirby fan (albeit I might buy one for a small price at a garage sale or a thrift store). So a Heritage is not worth much to me.
On the other hand, there are individuals who are very interested in anything with a Kirby label--and some even have a fondness for those manufactured in different eras or decades such as the 1980s. To them a Heritage may be worth much more.
That being said, a vintage cleaner's overall condition--including its motor, bag, wheels, bumpers, et cetera--along with its contents such as an owner's manual, cartons, and attachments could increase or decrease the interest of a potential buyer.
This is why you will see such a wide spectrum of prices for vintage items online or offline.
In closing I quote Margaret Wolfe Hungerford (née Hamilton), who wrote many books, often under the pseudonym of 'The Duchess'. In her novel MOLLY BAWN, published in 1878, there's the line "Beauty is in the eye of the beholder" (the earliest form of which can be traced to the Greeks in
3 B. C.).