The way I've had it explained to me is that the pricing is high because the Japanese market will bear it, and so lowering the prices on the Japanese market would hurt profits. When they've experimented with selling U.S. DVDs cheaper, Japanese fans have imported them at the lower price, killing sales of the more profitable Japanese region version. One way they've attempted to mitigate this is to make the DVDs unattractive to Japanese buyers using the methods you describe such as having dubbed audio with no Japanese sound option, or delaying the release.

edit: the japanese market's willingness to pay high media prices is explained on page 2 of the article