We used flexible desks for years as a consultant shop, but where given actual offices and could easily reserve meeting rooms. That's a much better cost / productivity trade-off.

Really though the cost of office space vs people making 100k/year means you don't actually need top optimize it that hard. The core problem is they tend to come out of separate budgets, so some middle manager can write down they saved x million on a review / resume while costing the company 3x that indirectly.

PS: Used Model S's are also something to keep an eye on.