When you consider the hoops SpaceX was made to jump through by the environmentalists as part of the FAA licensing process (detailed in the post here on 2022-06-13, “FAA Releases SpaceX Starbase Programmatic Environmental Assessment, Finds ‘No Significant Impact’ ”), one can scarcely imagine how they would have reacted to a proposal to launch Sea Dragon from the Gulf. I’m thinking something like the closing scene of Kingsman.
Also, according to the Wikipedia page on Sea Dragon, “Payload costs, in 1963, were estimated to be between $59 to $600 per kg (roughly $500 to $5,060 per kg in 2020 dollars. TRW (Space Technology Laboratories, Inc.) conducted a program review and validated the design and its expected costs.” Now, that’s a pretty wide range for a cost estimate, but Elon’s goal for Starship is much more ambitious: “Musk has predicted that a Starship orbital launch will eventually cost US$ 1 million (or US$ 10 per kilogram.” Even if he is low by a factor of ten, that’s still one fifth the lowest estimate for Sea Dragon.