Hi Tom,
Best answer I can give you about the cost of the ID41 is an answer I received long ago from a Far East manufacturer that we approached about making a particular part for a client.
His paraphrased response went like "We can make you One for a million dollars... or we can make you a million of them for $1 each... either way, it'll cost you a million dollars".
A "network card" to fit to the proprietary back plane of an 861 would only sell in small volumes and therefore that will raise the Unit Price.
I would also re-iterate that when we're buying Meridian kit, a very high slice of what we're paying for is initial design, development testing, listening time, fine-tuning time etc., etc. until Meridian arrive at a Prototype they are happy with.
Then the prototype needs to be documented, validated and the the manufacting procedures tested to make sure that Production units match the expected performance that was achieved from the prototype.
Given the small number of units that Meridian sell, these large development costs cannot be simply amortised over high unit volumes, resulting in the high prices we see.
As to your other question, I do believe that Meridian are aware of the potential benefits that Ethernet transfers might offer when connecting Sources to DSP's.
As remarked by Nick & Ian though, the issue that needs to be overcome is Synchronization between 2 to 7 DSP's and will not be an easy nut to crackI think.