I love this show. And yes it is expensive. I wanted to get into collecting and watching the older series on DVD, but the prices on those discs are high as well. That price at CC is a steal at less than $60 for both series 1 and 2. Series 3 though youll probably have to buy on its own.
Really though, even with the high price, I dont feel cheated because of the quality of the show and the special features. There are commentaries on each episode and behind the scenes, deleted scenes, and tons of other stuff.