SABRE engine is not really upcoming. It never even got close to production or prototype. And the estimate cost of that vehicle were very optimistic with lots a

SABRE engine is not really upcoming. It never even got close to production or prototype. And the estimate cost of that vehicle were very optimistic with lots and lots of problems to overcome. A proposal like that from people who have never really done all that much is highly speculative. The projected cost they could reach with that vehicle, is already beat by Falcon 9. Elon Musk has even told the Royal Aeronautical Society that he thinks air-breathing engines are a bad idea. Massive complexity for not so much gain. Invest that money into better first stage engine, push threw the atmo quickly get out of it, and make optimal use of your second stage engine. Its pretty save to say SpaceX will not invest in what is mostly a paper rocket with an engine that has only ever tested the cooling system.