Ya, and restricting airflow reduces load. It may not be intuitive, but you can plug a vacuum cleaner into a meter and put your hand over the tube to restrict airflow. The load on the fan will go down because less air means less friction. In other words, it's easier to run a fan inside a vacuum. The louder sound you get when you put your hand over a vacuum cleaner tube is the motor speeding up because it has less load.
Maybe our disconnect is that we're talking about two different things, one being the rated design point of the blower system, which is presumably constant (though newer systems seem to be more sophisticated), and the other being the exact load and power consumption that depends on backpressure. A higher backpressure will certainly increase the motor power consumption on a classic induction motor - if not by 100% then by some non-zero amount.
Anyway at the end of the day I agree with the original characterization of wear and tear - motor and blower will probably outlast most other components. In the case of the one I mentioned this seemed to be true. You just may end up paying a little more for the electricity to run it.