Assume every motor has a 1% failure rate per year.
A boring wheeled roomba has 3 motors. That's a 2.9% failure rate per year, and 8.6% failures over 3 years.
Assume a humanoid robot has 43 motors. That gives you a 35% failure rate per year, and 73% over 3 years. That ain't good.
And not only is the humanoid robot less reliable, it's also 14.3x the price - because it's got 14.3x as many motors in it.
[1] And bearings and encoders and gearboxes and control boards and stuff... but they're largely proportional to the number of motors.
Plus they'll likely be modular and able to be replaced.
IMHO, the bigger design issue for humanistic is lowering the need for mechanical precision which requires lots more metals and instead using adaptive feedback and sensors to obtain accuracy similar to how humans and animals do it. AIs should be really good at that, eventually. I think the compute will need to be about 10x what it is now though.