>>12998159too lazy to look up the numbers but iirc the saving is only like 150 m/s or something really tiny, atmospheric drag in total is a fairly small component of the cost and rockets don't spend much time at low altitude anyway so launching from mountains just makes logistics a pain and doesn't give enough of a benefit to be worth it
plus you generally want to be launching east and from a coast if possible so you don't drop stages on villagers which already limits good launch sites a lot, trying to find good mountains too will really fucking limit your options
