Comment by artimaeis

Maybe someone else can say with certainty, but I will note that they chose a > 1m cable to image. Thunderbolt 4 cables <= 1m in length can be passive, Apple's 1m cable is only $69 USD.

That probably explains the irregular pricing intervals stepping up from 1.8m $129 to 3.0m for $159. Though it's a very Apple thing to charge $30 for the extra 1.2m of cable. At least the complexity of the integrated circuit can explain that first jump.

I'd imagine both the very-high bandwidth and the PCIe interop make necessary the retimers.