The resources below break out the resources with advertising cost and media usage (audience reach) for each type of media. Finding costs and reach is difficult as some companies don't make this available to the public.
Media kits are websites or brochures media organizations create to sell advertisements on their media properties. It may contain information on their audience, editorial calendar, and advertising rates. Look for a media kit by using an internet browser search engine (e.g. Google) to search for the media company's "media kit" (example search: Vogue Media Kit)