When TFA talks about semiconductors it really only directly compares it to silicon, when GaN is probably the nearest competitor to diamond, both in cost and per

When TFA talks about semiconductors it really only directly compares it to silicon, when GaN is probably the nearest competitor to diamond, both in cost and performance. I believe diamond is "only" about 20x the cost of GaN; anyone know what the economics would be for substituting diamond for GaN in e.g. HVDC?