Actually episodic TV shows don’t cost all that much compared to feature films. Their typical cost runs from 1 to 3 million dollars an episode. That’s a couple of million bucks for 45 minutes to an hour’s worth of show. Feature films by comparison cost 30 million or more for 2 hours’ worth of show.
For the CSI franchise shows, especially the original, the fees for the cast members and writer-executive producers are enormous. But that’s a function of the shows’ success and their almost guaranteed top ten position in the weekly ratings.
In order to put out an hour long show with the high production values of a Criminal Minds, Mentalist, Fringe, et al, you need to pay a highly skilled union crew for eight days. Long days which often run into overtime. The audience, both US and global, expects a certain look which is only attainable by careful, time consuming lighting and precise camera work. Any time the camera moves it costs in terms of setup time and rearranging what the camera sees. Action sequences like those in Buffy add another layer of cost and difficulty. (My coworkers used to call the show Buffy the Weekend Slayer.)
The audience also expects realistic effects, crowd scenes (requiring extras at a union rate of $120 a day and a non union rate of $60), and the occasional outdoor scene to break up the indoor monotony. Outdoor scenes require trucking the entire production to the location and back, renting the location, and paying everyone for their work and their transit time. The audience also expects good quality hair, makeup, and wardrobe, not to mention special effects.
All that said, it’s possible to do an hour show for much less. Soap operas, for example, shoot an episode in roughly a day. But their production values aren’t nearly as high - they just don’t look that good. Even a night time soap can save a lot of money by always staying inside on the soundstage, and sticking to a limited number of sets.
Time is the real killer. The longer it takes you to do something, the more it costs. Careful lighting and tricky camera work give a show a much nicer look, not just better picture but more motion and verisimiltude. This all costs money more money.
Studio backed feature films are typically shot much more slowly and carefully than TV shows are, so the costs are greater by an order of magnitude. A TV show shoots in eight days. A feature shot in eight days is super low budget.
http://www.businessweek.com/magazine/content/08_18/b4082054975746.htm?chan=magazine+channel_what’s+next