A 10/100 port is less costly to implement and is sufficient for the amount of bandwidth needed to get the music to the endpoint. The store has the potential need to service multiple endpoints which requires more bandwidth and therefore the 1Gb interface. Simple economics, no conspiracies.
Is a 10/100 significantly cheaper on a device the cost of an MS600? I very much doubt it. And if so why does my �200 printer have Gigabit ethernet? Surely they would have cut costs on that if it made any difference at all.
Networks are reliable if properly installed. If noise on the line was a major problem then you wouldn't see them used in business. A properly designed network interface can tell the difference between a data packet and noise and reject the noise.
Sure, no-one is talking about that kind of noise or problem.
Network jacks are grounded so EMI on the lines are prevented from getting into the device.
Then why is Meridian using ferrite cores now on LAN cables, and why are there ferrite cores on cables at all (I mean in any application, at any level), if simply grounding the plugs blocks any RFI getting into the device? It seems to me you have just stated that ferrite cores make no difference to anything.