I imagine there are those who, knowing of the quality of Hoovers from the Good Old Days -- especially the Convertibles, the most practical models for day-to-day use -- would be delighted to find one "brand new in the box" to put to good and regular use.
I can't tell you how many times "older" people have told me that they wish they had the Hoover, Eureka, Electrolux or what-have-you that they had when they first set up housekeeping 40 or 50 years ago, because most of the new machines are "cheap, plastic crap."
And, other than ruining the "mintiness" of the machine, there really would be no harm in even a collector purchasing one of these Hoovers and actually using it if s/he chose to do so.
I too have mixed feelings about the high prices that some machines go for ... but at the same time I don't begrudge anyone the right to spend what they care to spend if they have the money to spend. Who am I to set limits on other people's budgets and spending just because I myself am perpetually poor and can't afford to "spend with the big boys?"
Plus, there's a double-edged sword here: Those who list things on eBay certainly don't post begrudging comments about out-of-control eBay auctions when they get big bucks for THEIR stuff!
The idea that everyone should be on a "level playing field" with no one having a financial advantage over anyone else is nothing less than socialism, and personally I'd rather do without the occasional eBay treasure than to live in a socialist society. Even within the context of vacuum cleaner collecting. You want to talk about a double-edged sword!
Those who suggest that all collectors should feel obliged to adhere to some sort of monetary limit as to what they are spending (and, by the way, WHO would determine that limit?) really have not thought through what they are suggesting, I don't think.
http://en.wikipedia.org/wiki/Socialism