How much is it ?

I am pretty sure it's different for every state. Here, I think the fee was somewhere around 70 bucks, but it was paid for by the facility I took my class at.

Your best bet is to go to your state department of health (here is the link to California's: http://www.cdph.ca.gov/Pages/default.aspx )

They are in charge of certifications and whatnot, and you should be able to find the cost either on the website or by contacting the department. Just search for "CNA" on the site and see what comes up.