They can just swap for ferrite and have a lower power motor, but again, I think they will do more than that, because the savings can be much greater that way
You size a motor with the field strength you plan to run through it, if your field strength is lower due to weaker magnets, you can have less iron, way less iron, it's a linear relationship, so if you magnet is half of the strength and same size, and have half of the magnetic field density, so you can have half of the iron without driving it into saturation
If you just replace the magnets in the same motor, now you have double the necessary iron