I was curious about the actual cost of doing this.
Average annual rent $/sqft = $30 (US), $40 (Seattle), $70 (SF/NY) [1]
Average private office space: 196 sqft [2]
Average cubical: 90 sqft [2]
Price of upgrade: $3180 (US), $4240 (Seattle), $7420 (SF/NY)
Another way of looking at this is ~$2-4/hour.
This ignores that if you did actually give every developer an office, prices would increase due to lack of space. It also likely ignores a slew of other factors from the real world.