In my opinion back in the day there would only be one rookie card for a player. And now with a saturation of rookie cards everyone is looking for something to replace "the one" or a "true" rookie card and Topps Chrome seems to be it.
Strange hobby sometimes. I got a Lebron Fleer Ruby RC /50 and it would go to market for $300-$400. Yet a base Topps chrome which has been produced in the tens of thousands goes for $500-$1000.
Topps chrome initially had a limited Retail (I think) release, and was not readily available, in US as well as abroad.
After the first year however, with its success it became a mainstream release and they made plenty, but with the nice timing of it coming with Kobe's RC year, it set the tone for its exclusivity.
Cases are being hoarded. I know one guy who has 5 cases of the 03/04 release and every so often he either breaks one or hocks the boxes off on eBay. The 08/09 as well.