So I just looked up the prices on Mouser and Digikey for an amplifier or mixer in those frequencies, and boy are they expensive. The R&D spend must be enormous for them not to be making those parts in these frequencies as separate bits.
I mean, you can make a RADAR with a single transistor, 2 diodes, an exotic but off the shelf VCO, and clever transmission lines. I doubt the R&D cost is very high for for the MMIC here.
TI is making a 60 GHz RADAR in a CMOS process. I’m sure R&D costs were heavy, but production will be cheap.