A huge part of the collectable game experience is the collecting. Why then, do collectable game publishers work so hard to make sure their cards aren't collectable?
Restricting Play. Tournament systems that restrict what cards may be played. In many cases, entire sets are banned. Watch the card values plummet when they aren't legal in the most popular tournament format.
Reprints. Why reprint a card, ever? Make new cards that are as good. Don't steal from your customers by destroying the value of thier cards by reprinting them. If you must reprint, reprint the most common cards. Never reprint a card worth more than a dollar.
Disregard. Some game companies see the secondary market as something they have to steer clear of. Something they don't have control of, and can't be involved with. That's crap. Anything a publisher does to increase the value of the product is a direct benefit to their customers.
All three of these things must be considered when the game is created. One of the biggest knocks against collectable games are their expense, but they aren't nearly as expensive if you can get your some, all, or more money back when you're ready to play something else.
It's all about creating value, and collectable games have an unique potential for value, if that potential isn't wasted.