Why do people develop such a narrow focus? Well for some it's simply a matter of storage area and they keep a narrow focus because that way they don't have to build a warehouse just to store their collection and just maybe they can fly under their wife's radar. For other's it's something that they simply can't explain ... the desire to collect something very specific is just there inside their head and it's way too hard to resist.

Regardless of how narrow their focus might be everyone who is a collector looks for things that are unique ... sometimes only unique to them. They might also look for things that they have not been able to add to their collection in the past, things that are in good condition ... although they will settle for something that is in not-so-good condition if the item is rare and they don't already have it in their collection. And sometimes they'll buy something to add to their collection simply because it's a bargain.

But for a true collector price isn't always a major consideration. If it's something they want and something that they don't already have then they can go crazy in a bidding war to obtain whatever it is they want. You only have to spend a little time in one of the collectible areas of eBay to see how that works in reality.