I think that one of the smoking guns was cassette pricing. Cassettes have been phased out; won't have that problem again.
DVD sales are great because the prices are lower than CDs. If the entertainment industry wants to improve sales figures, they should get the hint.
For the last few years, CD's have been cheaper to produce than cassettes but they continued to incorporate a surcharge that was originally justified by them due to the higher costs of producing a CD.