Spybotics series still fall under the time frame (pre 2003) that they were not tracking cost very well and were only produced for one year.
The cost of the fiber elements may have a lot to do with the material they used and the machines and process needed to get the final product. Keep in mind TLG had to have new molds an possible a entire new machine or machines produced to manufacture these elements. Cost of the parts need to include the cost of the investment to make them.
Making a circuit board is cheap by comparison of setting up injection molding. China has dozens of plants that could have produced them by the thousands in no time.