It all depends on a ton of factors. The maximum bit rate for the video stream on a Blu-Ray disc is 40 MB/S. DVD was capped at 9 MB/S. Blu-Ray also has 8 MB/S available for audio. I am not sure what DVD's limit was.
Whether or not a studio chooses to use all that bandwidth (or needs to use all that bandwidth) depends on even more factors. The quality of the source (as it has been with VHS and DVD) is still overall the most important determiner of how good the video will ultimately look. But using the same source material and comparing VHS to DVD and then DVD to Blu-Ray you will notice a sizeable difference.
Yes, studios are typically splitting up TV shows on to multiple discs. Its really to your advantage (at least in terms of video quality) that they do this, because it will ultimately look better and better reflect the quality of the original source. Keep in mind that studios are still compressing the original source file (which is probably at least double the size of what is on the Blu-Ray). The more compression, the less it will faithfully reproduce the original. Multiple discs obviously do drive up costs a little, but there isn't really a point in buying the Blu-Ray if they are going to compress the hell out of the video anyways.
The bit rate on a video will vary, and it will typically be higher on "high action" scenes and lower on less intensive scenes. This all depends on each individual encode though and there are no hard and fast rules. Its ultimately the studio making the encode's decision.
Every encode is different, and the demands of encoding different types of movies (action movies, slower drama movies, animation movies, etc.) are different. I am really not going to get any more in depth than that unless you actually know something about video encoding as it gets pretty complicated.
Expecting Blu-Rays to cost as little as DVD's at this point in time is completely unrealistic. That would have been like expecting DVD's to cost the same as VHS's. Costs will naturally go down and you will see things hit the bargain bin. For example, I can sometimes buy a Blu-Ray on Amazon cheaper than I can actually buy the DVD. But at this point in time, Blu-Rays are simply going to be more expensive. That's just how new technology works and it is the only way to keep it sustainable. Studios have no incentive to make Blu-Rays if they can't make extra money off of them. Otherwise they would have just stuck with DVD's.
We had two bags of grass, seventy-five pellets of mescaline, five sheets of high-powered blotter acid, a salt shaker half full of cocaine, a whole galaxy of multi-colored uppers, downers, screamers, laughers…Also a quart of tequila, a quart of rum, a case of beer, a pint of raw ether and two dozen amyls. The only thing that really worried me was the ether. There is nothing in the world more helpless and irresponsible and depraved than a man in the depths of an ether binge. –Raoul Duke
It is hard to shed anything but crocodile tears over White House speechwriter Patrick Buchanan's tragic analysis of the Nixon debacle. "It's like Sisyphus," he said. "We rolled the rock all the way up the mountain...and it rolled right back down on us...." Neither Sisyphus nor the commander of the Light Brigade nor Pat Buchanan had the time or any real inclination to question what they were doing...a martyr, to the bitter end, to a "flawed" cause and a narrow, atavistic concept of conservative politics that has done more damage to itself and the country in less than six years than its liberal enemies could have done in two or three decades. -Hunter S. Thompson
