That's weird. So you're suggesting the seller is banking on getting more for a low grade note simply by listing it as a counterfeit?
That is
exactly what I am suggesting. Low grade common series notes are worth very little if anything above face value. One thing these types of notes are used for is experimentation in basement laboratories. Y'know, by people trying to learn to clean and press. These notes tend to be low grade and have a fishy appearance. Not coincidentally, counterfeit notes are expected to be low grade and have a fishy appearance. The $5 note shown above (which sold, BTW, for over $60) shows evidence, IMO, of cleaning/pressing. Another of the seller's notes, a $1 note with the serial numbers almost entirely missing, is likely the result of exposure to bleaching agents. If one looks closely at that note, one can see residual evidence of a serial number previously printed on the note.
LOL. I can see the eBay negative feedback already. I paid for a counterfeit note and he sent me the real thing! What a ripoff!
Yes indeed, that would be quite funny, but in reality, the buyer is completely handcuffed. He/she can't return the note or complain to eBay afterward.
OTOH, maybe there's a secret market for 1954 counterfeit notes.
There very well could be, and I am aware that there are avid collectors of counterfeit Canadian coins (the period counterfeits - not the modern stuff from China). However, I would expect the taboo of collecting fake paper money to be much more significant. I don't think anyone has gone to jail for having a few old 50-cent pieces made out of lead metal, but fake currency is a serious matter to the Bank of Canada and to the police. Maybe the high auction prices are due to the realization that counterfeit paper money is inherently "dangerous".
Twenty years earlier, the Nazis were producing counterfeits of Bank of England notes. Today these sell on the collector market for more than their genuine counterparts. 
Another example would be 18th century British copper coins produced in North America, like the so-called "blacksmith tokens". Just like your example, there was a historical precedence for the counterfeits to be produced, and that's why they are collectible to the point of outstripping the originals in value. But most counterfeits don't accrue high values over time. I don't see any historical precedence for fake 1954 series notes, do you? They might seem interesting, but as the eBay auctions demonstrate, it would be all too easy for someone to claim a note is counterfeit and attempt to make a profit from it. Since most collectors can't learn to grade, it's not surprising that they also can't seem to tell the difference between real and fake. And therein lies an opportunity for exploitation. Anyone could take an old note and hand-cancel it the way some notes from broken banks were cancelled to prevent possible future redemption.
Realistically, though, I don't expect to see a bunch of copycat auctions. For one, dealers are not going to risk their reputations selling counterfeits. Secondly, like I said above, most collectors just don't know real from fake, original from processed, etc. So it would not occur to these people that they could take a fishy-looking note and represent it as being fake.
