the bandwidth costs for distributing long-form video are much greater than a 3Mb aac music file. the profit potential is much harder to find for video than music since i don't think people are going to pay a lot of money to get shows they can get on tv.
Bandwidth is pretty cheap. Prices for large users (like Apple) are <$1/GB. So an H.264 SD 1 hour TV show should cost less than $0.40. I think that for a 30 minute show Apple could swing $1/episode. For an hour, up it to $2 or $1.50. For a movie, you have to come in line with DVDs to cover the royalties so you're probably looking at closer to $10. But I think $2 for a 1hr show is comfortable for consumers.
Keep in mind that Apple has been springing for bandwidth for trailers for a long-ass time and getting no money outside of derivative sales from QT Pro, etc. I don't think it's insurmountable.
For royalties on TV, season DVDs appear to average $1.25 to $1.75 per 1 hour episode. Taking out packaging, distribution, retail cut, etc. you are probably looking at $.75 or less per episode in royalties, which is close to what the music labels get. I doubt that episode downloads would significantly cut into DVD sales and I think consumers would pay MORE for TV download than the DVD bundle due to the timing convenience.