I appreciate that Canada is leading the global air travel world in this space, with the one-person, one-fare policy. It is not the case in other places. This is something that is unique to Canada.
I will recognize that inter-jurisdictional issues and business competition issues add complexity to this, but from a purely accessibility perspective, I would suggest that, at a minimum, if a carrier requires a person with a disability to travel with a caregiver, then that person with the disability should not be financially disadvantaged by that requirement of an airline.
It is difficult to balance all of the challenges here, but yes, people with disabilities are often faced with additional costs. The costs of their equipment alone are different from what someone else would deal with. The cost of travel is definitely often more than for others.
Certainly, if the requirement to have a caregiver attend is the requirement of the airline, then it should be at their cost.