[Duncan]

To expand on Kevin's post

The Tesla Model S/X 'small' front and 'small' rear drive units weigh ~90kg and produce ~220kW/~300HP peak.

That is the drive unit - it includes the reduction gearing, the diff and the inverter - 31Kg for the actual motor sounds about right looking at it

 

[Duncan]

It doesn't sound right to me. But it is strange how the value 31 came up. If I were to make an estimation I would use good round numbers like 30 or 40.

Anyway. In that assembly, I would expect the controller to weight not more than 20 kg., and even that seems to much for me. The reduction gearbox in that case would have to weight the remaining 40 kg. (39 to keep up with the exact number for the motor) . But this seems way too much for just one stage transmission. A normal five-speed manual transmission (for FWD) would weight about the same, and that one would have five times more gears plus the reverse.

Has anyone ever disassembled a Tesla drive-train and measured the motor?

You forgot about the diff - and you do need a bit of metal to handle those power/torque numbers
Comparing the reduction gear for 300 Hp to the gearbox for a 100 hp FWD car is a bit thin