content: Not necessarily. The best illustration is when there was a big panic about a year or two ago over the availability of the rare earths. The main supplier was China, but behind that situation was a history of where China deliberately undercut other suppliers so as to achieve almost monopoly status in supplying the materials. Then China tightened the screws for political reasons. This set off a big (almost) panic, and alternative sources were looked at intensely. One was a disused site in the USA if memory serves me well. I'm afraid I don't know the present status of the elements in question, but the incident was instructive. The point is that neither 'cost' nor 'usefulness/efficiency' can be looked at in isolation from other factors, many of them geopolitical. The 'free market' in materials such as these is often very complicated due to such other factors.