Advice on High End Card purchase

[hcv123]

The underlying factor to this questions is one of basic economic theory (of which I remember very little about, but will be happy to offer my opinion anyway). Price being the variable - if demand is greater than supply price is driven up. If supply is greater than demand - price is driven down. Time is another relevant factor in this conversation. Today baseball cards are widely collected - part of a sport that is our national pastime, etc, etc. An important question is - is the fan base for baseball growing or shrinking? A growing base would lend itself to a position that baseball card collecting isn't going anywhere and in fact is sustainable for the short to intermediate future. If the fan base is shrinking, it would definitely cause concern for the intermediate but perhaps not the short term.
I would prefer to take the risk with an item I know to be in short supply of the most collected player(s). While often times there is less demand for them, I usually only need 2-5 people interested to get some price appreciation (as in the case of the Venezuelans). Something like the Mantle rookie from a supply stand is much more risky over time- why is the market climbing - are there really that many more people willing to pay that much more for it? Is it being driven artificially in some way? Assuming all is legit - what happens to the price at the point where demand starts to fall and the supply is so plentiful? All of that said. Time will tell.