The argument for CON is that if a new facility came in and charged less, then the existing facilities would have to charge more to cover the patients they lost which would adversely affect their remaining patients. So a new facility would need to show the need of non-served patients - ie that they wouldn't take away patients from existing facilities.

It is of course hogwash, but is a nice way for existing facilities to have a monopoly, prevent competition, and not have pricing pressure. Standard rent seeking/corruption that exists in the US.