Typescript is miraculously productive on the front-end as soon as you've got people writing at different "layers"—someone writing a frontend library, someone else handling state and actions, someone writing components for re-use, someone making it look pretty and using those components. You can be sitting right next to someone using code you wrote but rarely need to discuss it because the types communicate everything so damn well.
But when I started using it for backend and infra, the iteration speed is much slower, so even TS only saves a few % of deploys, it's still a noticeable amount of absolute time.