I love westerns and agree with many that Deadwood was quite wonderful. They must be rather expensive to produce and film and that's probably why we only see the handful of movies every few years.
I don't see why a TV Western today would necessarily be more expensive to produce than any other dramatic series that uses a few standing sets and a certain amount of location filming. In fact, one reason American series television was dominated by Westerns in the 1950s and ’60s was that they were relatively cheap to produce. Every movie studio had its backlot frontier town. Every wardrobe and prop department had a large inventory of period clothing, guns, furniture, wagons and other acoutrements. And the "horse opera" provided almost limitless story possibilities. The lone hero or the core of regular characters could be written into just about any dramatic situation.