Totally depends on the company...
Delta - costs nothing. But they are the worst in the industry for supporting pilots in it.
American - probably costs the pilot 30 percent? Some companies about half? Hiccups are the pilots problem, you don’t just get fired.
United somewhere in between, but VERY lifestyle invasive.
NO MATTER the company, you are well advised to steer clear of these amateur run control scams. If you get cancer would you trust a doctor the company hired without so much as a second opinion? THAT is precisely the situation.
If you are 121 and being approached by these folks... take a medical leave of absence and hire a REAL lawyer. Steer clear of ALPA and APA (AMAS).