The cost difference is due to patents, not on the drug which is old, but on the damn inhaler. That may be done now, IIRC protection ended in 2021, but I'm not sure off the top of my head if they have generic albuterol inhalers.

As for the prescription, I'm sure some hypochondriac thought people would find a creative way to help themselves get high with it. The other argument is that it's not a good treatment long-term if you've got asthma. If you're using the inhaler too much, you'd be better off on a stronger therapy, so they gatekeep a bit to ensure you're going to the doctor and getting escalated if your symptoms require it. These arguments are common reasons why some of this stuff is prescription. The goal was to provide people with better care and not encourage self-medication.