I don't think a Chris King is dramatically better than other high-end headsets, especially if you're good with maintenance, but in addition to being an excellent product, there are some non-performance reasons to buy CK that others have mentioned above.

I'd love to able to buy a bike where everyone who'd contributed to its production was paid a fair wage in a safe and environmentally sound facility, but I'd need to be Bill Gates. The happy/sad fact is that we've gotten used to things manufactured by folks making pennies a day. Happy because it puts technology in a greater number of hands for a lower price, sad because that equation demands that someone be on the losing (pennies a day, exposure to all sorts of nasty stuff) end of it.

I'm not trying to get all mushy and claim I'm saving the world, but if I can purchase a quality product made by people who are passionate about what they do, and paid a living wage to do so, and the product has as minimal an impact on the environment as is reasonably possible, well that's worth an extra $50 or $60 to me. But, it's totally cool if it isn't worth it to someone else.

So the short answer: It's a quality product that has additional non-performance related benefits that make it an attractive purchase to certain people.