It’s not an extra cent for a closed loop cooling system and your straw analogy is closer to closed loop in how it works. They use open loop because vaporising water takes a lot more energy than heating water. You get a lot of more cooled. The alternative is to run a ton more AC at lower efficiency since the hot side of the AC won’t be cooled fast enough. They’re doing it to use less electricity since electricity is expensive. In a way, it’s a good thing. Until you factor in droughts