I suspect that cost of CD has very little to do with cost of printing or distribution. It is most likely based on demand and price manipulation. Printing CD is perhaps $1 while royalties to artist are not more than that. Double that for distribution and we have $4 CD. It is controlled by few companies who set prices as high as market can bear. When CD is less popular it becomes $8 instead of $16. DVDs sold in US are sold in China for much less. 20th Century Fox admitted making small profit after selling them for equivalent of $2. The only think that stops people from importing Chinese DVDs back to US is regional code of DVD preventing US sold DVD player from playing them.
Downloading CDs will be much easier and no out of print issue, I agree, but downloads can take long time. My home internet is running at 3 Mbits/s. In case of extremely long 80 minutes CD (700MB) it will take an hour to download (assuming top speed without interruption or slowdown). Perhaps when artists decide to sell downloads themselves (some already do) it will eventually reduce cost to possibly less than $5 per CD.
