Where flexibility pays for itself
Flexible workspace is priced at a premium per seat. That premium is worth paying where the alternative is committing to area you may not need, or waiting months for a fit-out before a team can start work.
It is not worth paying where the requirement is stable and long term. A predictable team of a hundred people in a city you are not leaving is usually cheaper in dedicated space, particularly once the flexible premium is extended across a five-year view.
The useful question is not flex or lease, but which parts of the portfolio should be fixed and which should stay flexible. Most organisations end up with a core of dedicated space and a flexible margin around it.
