The cost is more about the approval process, not the piece of equipment. The approval process is so long, that the electronics are hopelessly outdated before it ever comes to market.
Look at the FMS, the 'upgrade' is to 1 MB of memory, which your cell phone has more...but just try to market a new one.
We are working on the RNP redundancy requirement, because in some airports, such as in China, the only way in/out is RNP, and if you lose one, technically you are not allowed to use the RNP procedure, so you are really stuck.