There are several online price guides for old magazines. Amazon, iGuide, Downtown Magazine, eBay and XYZ Collectibles all have sections offering price guides for vintage magazines.
iGuide is a searchable database maintained by the Old Magazines Price Guide. The database contains detailed reports on estimated values, including a section that shows actual prices that were fetched at live auctions. iGuide warns sellers to keep in mind that prices listed are strictly estimates. Actual selling prices may vary from region to region. Sellers should be prepared to receive offers between 30 and 50 percent of the retail selling price, depending on the condition and quality of the item.
Amazon offers Kindle and paperback versions of Antique Trader Vintage Magazines Price Guide. The guides are available from third-party sellers but shipped via Amazon. Subscribers can read the magazine for free.
Downtown Magazine offers a collectible magazine back-issue price guide. Its newsletter highlights articles and publishes excerpts from old editions of popular magazines such as Sports Illustrated, Life, Esquire and Playboy.
A section listing vintage magazines up for auction as well as several price guides for old magazines is available on eBay.
XYZ Collectibles has a selection of National Geographic magazines dating back to the 1800s.