I think most people that really like a show think like you do and that is the way I feel to (the whole movie vs. TVonDVD) but the problem lies in the fact that other shows that have been on the market shorter than Star Trek: TNG and have gone lower to scoop those off of the fences.
IMO, the problem lies in the bins for cheap movies you speak of. People do see the movies in the bin and instead of buying something they may like more than what is in the cheap bin they'll buy what is in the bin and wait until the other movie goes into said bin and buy it.
This is what is happening with TV on DVD. Granted there are probably people that will pay full (or near full) price for the show they liked but people see other shows on sale and some will wait until the show they want is on sale and buy it at that time.
So you see I believe that there are people out there who will pay full price for something and there is also a group of people that believe that full price isn't worth it. And if they believe they can wait and pay significantly less they will wait.
Meanwhile, if it is a new show on DVD, and their just is not enough people buying at regular price than the company making the DVDs may not make more because the consumer decided to wait for lower prices.
Eric, who knows that X-Files and Star Trek are not like any other show. Who also knows that long "sentences" are cool.
Eric, who really likes Jeff*H's idea of dropping the price of the first set to draw those on the fence to buy Season 1 and decide to buy more. Problem is, most people think that Season 1 and 2 of TNG are not the greatest