Slayer’s playing the WaMu Theater with Megadeth on January 18.Every time I see a “recession” special, a part of me wonders, “Are we talking financial recession or a recession of interest?” Remember when acts like No Doubt had to practically give away lawn tickets at White River Amphitheater over the summer? Now comes word that Slayer and Megadeth are co-headlining a tour — American Carnage, opening at the WaMu Theater on January 18 — together for the first time since 1991’s “Clash of the Titans” tour. To ease the pain at the turnstile, a “chunk” of tickets are being sold for the 1991 price of $10.Recession or not, is this tour worth $10?