I don't remember the royalty but I remember really well how the NTK killed the finances of a friend and me who wanted to get started with Newton dev right when the MessagePad 100 was released. Plus we had to buy a Mac (Quadra 610?) which also cost a lot. We talked to Apple Germany and the product manager told us if the cost is a problem then they didn't want us. They only wanted "professionals", no amateurs. Big mistake. I guess Apple always had a slightly arrogant touch :-).

I remember there was a C++ dev kit eventually but at that time the momentum for Newton was already gone.

It makes me kind of sad thinking about this. I think with today's connectivity and processing power combined with the ideas of the Newton devs we could have much better devices than what we have today. The iphone feels a little boring. Well made but boring.