The price does seem to have come down a bit and they are now about £65 for each or as a set of two, called a Teamset, you can save a couple of quid. Another option is Interbike and this one is nearer £149 per set. I think this is the one that Ian has.
Whilst these would solve the problem of communicating with my passenger and also give us both the ability to answer our phones, I have an older GPS that has wired output. I have had the Quest for over two years and as it works very well, I don't want to spend more cash in replacing it with a bluetooth enabled system, Zumo or similar. So the hunt is one for a bluetooth transceiver solution to replace the wired option. The units can also be paired with others so that you can in effect have bike-to-bike communication as well as rider-to-pillion. I assume the bluetooth protocol allows for a unit to unit link and that this is encrypted?
Before I put hand in pocket I need to see some more articles on them and see what the consensus is.