In a way, those can both be true simultaneously. Just from the assumptions that the "established powers" make more money by modifying the kid implies that even if modifying the kid's environment cost $0, it would "cost" them lost profits of modifying the kid.

Costs are relative, and I think the point remains that the kid's parents are relatively powerless to alter the kid's environment significantly enough to solve the adhd problem. Thus, the decision of the cost/benefit analysis of modifying the environment vs modifying the kid falls to the "established powers", also known as, collective society.