Nico Nico Nii!~
There are no more magazines that actually print prices of Pokemon cards anymore, as far as I'm aware. Your best bets for checking values are 1) Trollandtoad.com prices, 2) Making guesses based on eBay listings, or 3) using Bebesearch.com. Those are my primary pricing sources. eBay works because a lot of card sellers who sell cards for a living sell them via eBay. I'd say Amazon, but as far as I'm aware, there's no way to check the final sale prices of completed listings on Amazon.