They did not respond to competition from DVDs, Video Games, Internet, etc. The industry has denied that pricing is an issue, blaming piracy, downloading, CD burning, mixed DJ tapes, and even boy bands - anything but their broken pricing model.
And don't blame the Boomers; they tend not to be all that price sensitive on small purchases (See Starbucks (SBUX) 15.99 CDs as an example). Besides, Norah Jone and The Beatles are the only real Boomer fare in this short list.
Consider these CDs:
In the top 10, there is but one disc priced over $10 (11.99). Everything else is $10 per CD (or 20 per double disc). There are 2 in the top 15, and as you work your way down the list, the higher the price, the weaker the sales (more or less).
Quite frankly, I doubt this is a coincidence. If anything, I suspect it reveals that CD purchasers are increasingly price sensitive, given all of the competing entertainment outlets and technologies.