It is sold everywhere for $20 now; worth it just for SimCity 4 and its expansion.
Simcity 4 is still the best pure city building game currently on the market, even when compared to more recently released competitors. Though it is possible to buy just the original title for $10, the game really is not complete without the Rush Hour expansion. It not only augments and makes much-needed improvements to the original's transportation options, but also makes numerous other improvements to the game in general.
And finally, there is an extensive modding community behind the game, which has developed over the roughly six and a half years the game and its expansion have been out. It takes over the development effort that Maxis has left behind.
If you want to be at the helm of the most intricate and engrossing city simulator that's out there, definitely check this out. And anyway, it's only 20 bucks.