Weeeeeeeeeellllll, there is a general correlation between rarity and value, meaning the less common something is, the higher its value will be. The problem is that most stuff is simply not rare, and there is no guarantee that anything that is perceived to be in short supply today will ever become worth a lot more. Some "rare" notes have not only not gone up in value in the past 20 years, they have actually gone down in value, and by "value", I mean what you can expect to get for them, not what the catalogue tells you they are worth. Asterisk notes from the 1954 series had their day in the sun. There was a time about 15 years ago when different asterisk prefixes did not have different values. They were all treated as pretty much the same and only classified by the signatures on them. Then someone got the idea to track different prefixes and see what the highest and lowest serial numbers were for each prefixes. Lo and behold, it became clear that some prefixes were printed in smaller numbers, and that created an instant market in which every prefix had its own value. Naturally, the prices went up too quickly and killed interest by collectors. People who were used to paying $20 per note were not enthusiastic about suddenly facing a cost of $500 per note for stuff like *N/Y and *D/O. The only people who were interested were newbies and speculators, and like I said, the market went up too quickly, meaning lots of people bailed out of the market, and reception for these $500 notes has been absolutely frigid to the point that they are hard to sell at any price if they are not locked in a plastic tomb with a TPG grade of MS-65 or above.
Some notes are historically popular and retain their value better despite not being rare. I would dare say there are more 1935 series $25 notes in private hands than *A/G notes, but the *A/G note catalogues $450 in Unc while the 1935 series $25 note will cost you five figures in the same grade. So don't look at rarity as the only factor to motivate you to buy a note. If anything, rarity is something of a trap. Anyone selling a 1954 series Beattie-Coyne asterisk note will be quick to point out these notes were printed in small numbers, making them "rare", but the value of these notes has not gone up for a very long time. They are virtually unsalable at the moment.
The only Rarity that matters these days is a white unicorn pony...
{http://img651.imageshack.us/img651/9729/rarity.gif}
Canadian Paper Money
