It is not just Obamacare, as if that wasn’t enough, but a couple of years ago (I believe), the American Psychological Association successfully lobbied to have mental health benefits paid on the same basis as any other medical illness. Bad move on their part and issues like this feed into the increased cost. It is simply not financially feasible to cover everybody for everything.
The cost of mental health outpatient coverage/benefits is really negligible compared to just about anything else. Just office visits basically; related prescriptions, if any, are or aren’t covered according to other provisions of the policy, and many states limit the office visits to 10/year. Compare this to, say, a single kidney stone running $35,000-$50,000 in hospital.