I don't think people are saying everyone should have private offices, which I agree is not feasible from an economic standpoint. Nor have I seen any studies say

I don't think people are saying everyone should have private offices, which I agree is not feasible from an economic standpoint. Nor have I seen any studies saying that private offices justify the costs of themselves in increased productivity gained. But there are ways that offices can be designed to be less likely to disrupt your work. Maybe grouping a few people in a private office instead? Or set "quiet hours"? Have designated "quiet rooms" where talking is prohibited? I feel like there are a lot of things that can be experimented with or try that are not a huge expenditure. And I know putting a dollar amount saved on productivity with innovations in workplace design are harder to show, but I think it's a widely known fact that interruptions affect knowledge work and peoples ability to focus. So if someone who should be working on focus work is frequently being interrupted every 30 minutes by noises and people asking questions and it takes that person 15 minutes to get back into the groove each time, it's easy to see just how many wasted hours there will be.