You are obviously ignorant of the fact that letting the mentally ill roam the streets has cost way more than hospitalization ever cost. I saw a study once (when this subject came up after some other mass murder a few years ago) of the increased costs of emergency room care, sanitation and police, plus the lost wages, medical and funeral expenses of the victims and their families - and believe me, in-patient treatment was a heck of a lot cheaper.
Many if not most of the “homeless” are mentally ill, and if you live in any city, you can see how they have destroyed all public spaces and street life in many areas.
As for lithium, that’s way in the past, and having visited people who were hospitalized in the New York State system until deinstitutionalization hit in the late 1960s, yes, these places were quite nice and, in addition to often providing the only jobs in their remote Upstate towns, gave the residents a decent, dignified place to live. There were recreational programs, they lived in cottages with 24 hour care, and their medication was supervised. Some of them could stabilize enough to go into other programs, but most of them were going to be there for the rest of their lives, and it was certainly a lot better for both them and us than having them raving in a doorway somewhere and pushing people under the subway.
Deinstitutionalization opened the doors of all these facilities and allowed the inmates to flood into our cities. More than half of the mass shootings in the last few years were done by people who were known to be howling madmen. All of them should have been safely locked away without access to dangerous weapons, yet they were wandering the streets, free to destroy other people’s lives. Build new secure facilities and lock up the crazies within. I don’t care how much it costs. The alternative is to remove all dangerous objects from everywhere in the country so homicidal maniacs can’t get hold of them. And I for one am not interested in using blunt kindergarten scissors to cut paper.