Undefined. But at zero cost in every case I know of, in a multitude of countries. Be it a simple policeman driving into the middle of the desert to help a cyclist, to a complex joint, multinational, civil-military operation in the middle of the ocean, with aircraft and the rerouting of container ships.
This isn't true everywhere. E.g. in the alps you might be billed for rescue, particularly if you're not injured or in a medical emergency. That said, SAR insurance is cheap. Many alpinist associations and the likes offer it as part of their membership, which is often less than 100€/yr. There's no reason not to have it if you're going out into the mountains.
https://www.acrartex.com/survivor-stories/