Yeah, its pretty expensive: the fee has to cover the cost of a pilot, a plane and an instructor. One typical tandem jump (where you are attached to your instructor, to make sure your jump is safe) will cost about $150. A second jump might be an extra $50 - $100.
Skydiving can be an extremely expensive hobby. Intial jump lessons cost about $400. After you are certified, each flight costs $50-$90 per jump. In addition to lessons and jump costs, Sky diving requires specialized gear which can add hundreds of dollars to the overall cost. Any improved items like glide chutes also add to expenses.