My guess is that Prof. Solum is the only classical music fan in class, but most in the class should find this post interesting:
The DVD format is taking over the classical music world, especially opera:
Sales regularly hit 5,000 units, the standard break-even figure for classical CDs, and go as high as 40,000 worldwide, says Klaus Heymann, the Hong Kong-based head of Naxos International. Also, the hard-core classical community doesn't have to wait around for the video companies to finish issuing meaningless Luciano Pavarotti galas before going on to the real stuff.
Once a nightmare of regional formats, DVDs are increasingly universal (look for the "0" in the code box), though savvy consumers still need a specially doctored player to read all codes on discs available on European Web sites. Disc prices, which range from $10 to $35, are still unstandardized. The Deutsche Oper's Die Meistersinger is $39, but the Australian Opera's better cast sells for as little as $25.
Whatever the reason, even the most expensive DVD operas cost less than sound-only, full-price CD sets[.] (emph. in orig.)
My guess is that reasons are: (1) the market is new, (2) the format is unstandardized, and (3) DVD's must compete against established record labels. New markets are not as stable or efficient as robust, established markets. The newness of the market puts pressure on the sellers to reduce prices to pull other customers away from CD's and towards DVD's. There's an economic term for this that I've forgotten, but essentially, few people are going to buy both the CD and the DVD so the DVD sellers have to offer an incentive enticing enough to convince classical music consumers to break from their traditional buying patterns.