Here's a tip, go out to the local airport and ask for them. They throw them away since they have no use for them anymore. I saved $80 bucks on all US approach charts because they were just going to throw them all away.
actually, I went to a neighbor who is a corporate pilot and he gave me ALL of his old charts (high and low). Since they expired, he had no use for them. They are fairly recent, but I have found no problems with the scenery match-up yet and have been using them for a few months now.