As an effective marketing move to sell more CDs, a lot of labels offer free DVDs with CDs or a CD/DVD bundle at one price. The perception is that you're getting something extra. However, are you really getting something you'll watch as much as you'll listen to the album?
In some cases, the bonus DVD has a lot of great stuff worthy of repeated viewings. Some good examples that come to mind are Queens of the Stone Age's Songs for the Deaf and Ash's Free All Angels and Meltdown. Using live footage, some interesting interviews and well-crafted music videos, these extras are very worthwhile.
However, a lot of CDs come packaged with one lame music video, some boring behind-the-scenes stuff and still photos. This stuff is hardly worth the extra dollars (often $4-$5 more in total cost).
Now with the widespread draw towards the DualDisc format (one side of the disc plays like a regular music CD while the other side has DVD content) things are getting a little out of control. Case in point, I was confused with which version of Ben Folds' Songs for Silverman I should get. Look here and take your pick: do you want the DualDisc version only, a CD and DVD "deluxe edition" set or this web-only offer with the "deluxe edition" with the bonus CD of rarities, Songs for Goldfish? I chose the DualDisc version for a reasonable price. I found the 24-minute documentary about the making of the album on the DVD side a good viewing. I was satisfied with what I saw but I wasn't craving more than what I already got.
I wonder, how much is enough? How much promotional fluff can you handle before you stop caring? We all know the music on the disc is the most important, but extras can help speed up the process of buying now over buying later. Call us suckers, but stop confusing us.