Yeh, true about the useful torque point.

It would take more time to spin a motor up to 60k RPM. The question is how much more time I guess? In the heli world where most of my experience lies that is not an issue as the motor is running at a fairly constant RPM. My main point was that by running a motor at a higher RPM, closer to its limit, you gain torque through the gearing. If the resulting gain of torque is more than you need, then its possible you can use a smaller (and lighter) motor to do the job and gain some effiency by saving weight.

The iron/copper losses I refer to does pertain to the brushless motors we use (and DC brushed motors afaik). I found this article on iron losses which gets pretty technical, but probably explains it well. Found this too.