I understand a large margin on the device itself because that includes various software licenses and IP. Auxiliary parts that can't be used to rebuild a full device (as the mainboard is missing) shouldn't carry that markup as you've already paid for those licenses when you originally bought the device.
Yes, but that depends on if the licensing fees are per board or per device. And even if your contract says “per device”, you could still be taken to court by the IP owner.
You seem to be putting words in my mouth. Maybe you think I said that a 50% margin is unjustifiable? Well I'm not sure what to say other than please read my post again and note that I did not.
Not being different, as in the spare parts having the same margin as the full device, is good enough. In the past they've had some very big and unreasonable markups on replacement parts.
