I am afraid "Rachel" has many good points regarding the obstacles to collecting Chartered bank notes. Too many types is not a good thing. Super rare isn't always good either. Information about them is scant. I remember seeing them a long while back, and even having great offers from dealers to buy one, but turning them down.
Many years ago, I remember telling a buddy of mine that I collected paper money and he wanted face value for his one Bank of Commerce $10 (in good shape too) but I just couldn't do it. The reason: the whole field was just too unknown for me. The note was gorgeous-- and likely a good buy -- but I just didn't know anything about them.
And that was in the days when I hardly even gave a thought or care to reselling a note.
I always hear myself talk about the "market value" until I almost get sick of it....but it always boils down to that. Even for "character" notes that I collect for personal reasons (varied condition notes (not UNC) with odd numbers/ history/ dates stamped on them/ etc) I know I can sell with less hassle than a chartered (but the market for these are small since it's a note I find interesting for my own particular reasons). For chartered, I need a special audience- a specialist.
The majority of Canadians (and world note collectors) will want to collect a note which is redeemable at face even to this day (all BOC isssued notes). Scotland, US, England, Ireland, Canada, and a handful of other countries do this. That might not make a lot of sense to us collectors who value rarity-- but it somehow adds legitimacy to a currency. Such is not the case for chartered notes.
BOC and DOC notes have enough series, issues, and varieties to keep a collector occupied for years to come. Some of these notes come with images of national identity, scenes, or icons that strike a cord with the collector. Some Chartered notes have great reverse images but a lot have portraits of dead bank presidents/treasurers.
Collectors also like to have variations of specific denominations to collect. They want to find special serial numbers, change-overs, short prefixes, replacements, or errors. If 10 million notes were printed and you have a solid radar you know you have 1 of 10 special kinds of notes- an extreme rarity (out of plenty). Can you imagine the same kind of enthusiasm for a 2 digit Chartered? The problem is how does that make it that much more rare if there's only 100 or so notes anyway? Some of these (and provincial series) are indeed beautiful -- especially the large notes-- but as you say-- most come at a huge premium. Their almost priced out of market!
So these are just some of the barriers that face this small specialized market.
The only thing that I can see that might help this special market grow -- is some drastic kind of change in the BOC's monetary policy. That would mean things like: Canadian currency turning polymer/ and a huge influx of new paper money collectors. If that were to occur then there might be some migration into the chartered arena, lower catalogue prices, more info, and more demand.