God, I loved that Dark Sun map. It was one of the reasons I fell in love with the setting at first, I think. I wish I still had it - I keep my eyes open, but havent' seen one in years, and don't expect I ever will.
The problem with it, unfortunately, is that it was to perfect scale and had the locations of "hidden" sites, like the outposts of many merchant houses and the gold mines. Not to mention the city by the silt sea, Celik, Yaramuke, and the fact that the Ringing Mountains block the entrance into a jungle (supposedly a campaign secret).
In other words, you couldn't reasonably give such an awesome prop to the PCs. Which sucked.
I have made my own PC-friendly maps with tea bags and the like, and it's a lot of fun. Maps as props are probably one of the most useful things you could give to the players.
While I agree that they are probably super expensive to print and release to the public as part of your product, I wish we'd see more of them, as opposed to some of the gimmicky items we see in boxed sets - custom dice, cardboard terrain, metal doo-dads, or stickers (blech). About the only gimmick I've seen in an RPG that I've really liked were those dragonmark house removable stickers that came in a DRAGON magazine... I put one on my guitar.