At first, the discussion of the Beatles in last night's "Mad Men" seemed like just another example of the show's famous cultural set-dressing, much like the news update on Vietnam heard in the background of the same episode. Then, in the closing scene, Don Draper unsheathed a "Revolver" LP and cued up the song "Tomorrow Never Knows." The general reaction on Twitter was, "Whoa." That sentiment was immediately followed by something like, "How much did that cost them?" Answer: about $250,000, according to people familiar with the deal. That's about five times as much as the...