> If technology to "3D print" silicon chips becomes available, that will be the turning point.
I do see the point you're trying to make about cost of manufacturing, but there are already a number of "printable" circuits that a 3d printer can put together to build your own chips.
And whilst the kind of circuits I've printed onto clothes don't quite match full-scale chip production, it's an active area of research [0], so I wouldn't say it would be too long before it reaches consumer hands.
I do see the point you're trying to make about cost of manufacturing, but there are already a number of "printable" circuits that a 3d printer can put together to build your own chips.
And whilst the kind of circuits I've printed onto clothes don't quite match full-scale chip production, it's an active area of research [0], so I wouldn't say it would be too long before it reaches consumer hands.
[0] https://www.machinedesign.com/3d-printing/3d-printed-flexibl...