It really takes timing and patience to get the good deals...Tuesdays and Thursdays on Frontier tend to run cheaper. I'm waiting for flights 66 and 67.....straight thru, nonstop, from MCI. I talked to Frontier in DV and they will be running those routes this winter, but as Sandy aptly pointed out, they moved it from Sat to Sun for some reason. That is the only direct route from Missouri at this time (with no legs), but just not running until December.
If you have the flexibility of last minute booking, sometimes you can get a decent price on those direct flights.
(BTW, Sandy, my price I quoted was for two passengers