Asthma inhalers go for about $50-90 depending on your insurance.
Imagine the parents who have to have an inhaler left with their kid's teacher, plus the kid carries one, and they have to have one at home in case the kid loses one. And the various inhalers are NOT all the same, some work better for some people than others, depending on which propellant is used, how the nozzle is designed, etc.
So, you're looking at several hundred bucks per kid.
Adults can get buy with just having a couple of inhalers, but personally I think it is CRAZY not to have at least one back-up inhaler since sometimes they can get clogged, or the propellant can leak out and suddenly they don't work any more.
Asthma becomes life-threatening very quickly, which is why the companies know they can gouge the patients for this.