And most importantly, open space is cheap. None of the reasons you listed explain an open space containing 40 people working in different roles and teams, some of whom will never ever have a work related conversation.
dev-output-per-sq-ft is one thing that seems not to get mentioned very often. If you can put 4 devs together and get .3 productivity out of each, but with 1/10 the sq-ft for each, the idea is that the company is coming out ahead on ROI.