Access to lots of magazine rates is free online. Google a magazine title e.g. "Sports Illustrated" and "media kit" then scroll through for a link to prices a.k.a. rate card. Or go to adsprouts.com to find prices by category such as Health and Fitness.
Look in library databases such as Academic Search Complete for historical prices for national t.v. advertising. Key in “advertising rates” and ( “American idol” or NCIS or “Dr. Oz”). Change date to 1 year.
A Wall Street Journal article dated 9/12/14 pegs a 30-second commercial in top-rated A & E cable show Longmire at an average of $31,300 versus $69,500 for Mad Men in a recent season. Per this article, Longmire was canceled because not enough of its viewers were in the coveted demographic groups of 18-49 or 25-54.
Here is an excerpt from Advertising Age October of 2012 : "Last year, "Sunday Night Football" and "American Idol" were virtually neck and neck for top cost, but the average cost of a 30-second spot in "Sunday Night Football" in the 2012-2013 TV season is a budget-busting $545,142, up from $512,367 the previous season, according to Ad Age's figures. Meanwhile, the average cost of a 30-second spot in the Wednesday edition of "Idol" plummeted from $502,900 last season to $340,825. The average cost of a 30-second ad in Thursday's "Idol" is $296,002, down from $468,100 last season, according to the survey."
Super Bowl ad prices have continued to rise as this excerpt from a 1/18/2013 Forbes article indicates: Since Super Bowl I the average rate for a 30-second commercial has increased at a 10.3% annual rate ... versus 6.3% for the S&P 500.
A 2/2/15 Wall Street Journal article by Jack Marshall compares the cost of a 30-second Super Bowl ad at $4.5 million to reach some 100 million Americans with the efficacy of advertising in other media: Prime time TV, online video, print magazines, banner ads on websites, and social media. Ad-buying firms such as TubeMogul and Varick Media Mangement estimate, for example, that the same expenditure would purchase 800 million impressions on a sports-related site.
An anonymous executive predicted in a 15 August 2013 New York Times article that "Breaking Bad" would set a record for cable ad pricing by nearing spot prices for network TV hit shows (around $200,000 to $300,000 for 30 seconds).
Ulrich's International Periodicals Directory gives ballpark prices for print ads for SOME of the large universe of periodicals it covers. For example, here's a screenshot of the ad price info for Vogue. Do a title search. On the next screen, scroll down to the Demographics link.
For radio station ratings in metropolitan markets, Nielsen's free website Topline Ratings is a great source. Set up a free account, enter the desired city , and compare station ratings (average quarter hour persons or AQH)
AdAge.com: Contains industry data such as Leading National Advertisers, Top Megbrands, Leading Media Companies, and Agency Report. Some of the data is only available for a fee, but much is freely available.
Advertising World: Provided through the University of Texas at Austin, Department of Advertising. An extensive collection of advertising and related links. Some are freely available. Others require a paid subscription.
Ad $ Summary (Leading National Advertisers): Listing of companies showing how each allocates its advertising among various media (print, televisions, etc.) Figures are given for individual brands. Located in Jerome Library Main Reference at REF HF 5801 .A18x.