There are large expenses in maintaining air traffic control towers - hvac, facilities, engine generators, etc. Also, air traffic controllers are paid high salaries. NATCA would like you to think they are suffering and poor, but the public is not that ignorant.
With today's high speed technology and redundancy capabilities, it is possible to simply have a few poles with video cameras placed around the airport, instead of having a control tower.
To save even more money, the Radar feeds, video feeds from the cameras, radio feeds, and all data feeds can go through high speed fiber backbones to centralize air traffic control at numerous airports. We could have just a few or one large location for controlling traffic at the nation's airports.
We could even outsource this job to India, where the pay is less and they have high speed network capabilities to operate in near real time.