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Sea Dragon [1] is slightly similar to that.

Fuel is a small part of the cost of a rocket, most of the cost is in the engines and structures. Cheap production of hydrogen or oxygen is unlikely to make things much cheaper.

Also, any mass left over at engine cut-off requires a large quantity of fuel at lift-off and possibly necessitating a larger more expensive rocket. This would make re-purposing of boosters in orbit less likely.

[1] https://en.wikipedia.org/wiki/Sea_Dragon_(rocket)