To answer your question - we don't know. If they use an expensive grade of refined copper, such as oxygen-free electronic (OFE) grade copper, then it might cost that much. My guess is it is just standard grade copper (the kind they make wires out of) and you are simply paying for the expensive marketing and packaging associated with these types of mineral systems that claim to "save you money"...
TFP does not advocate the use of any form of alternative sanitizer systems that use metal ions in pools. In the long run they will often lead to metal scaling problems in pools and they are an ineffective sanitizer at best (even when used in conjunction with the prescribed low levels of chlorine). If you wish to do so, you can type the term "EcoSmarte" in the TFP Search box (it uses Google to search the TFP discussion forum) and you will get 285 results of conversations regarding this product and the bogus claims that they make. Most of the posts are from people fed up with the EcoSmarte system and desiring to change to chlorine.
Good luck to you and I hope you can find a cheaper alternative to overpriced copper.