Not sure, are you comparing the costs of technology 50 years ago with the costs of today's technology? That's not a very valid comparison, to say the least. Not only technology as a whole evolved a lot to give you waaay more bang for the buck, but also everything done today is built on the shoulders of the giant investments made at the start of the space age. So please, let's not bring unfounded arguments for the sake of ideology.
Not 50 years ago. See SLS for example. NASA is paying $146m PER engine (and the rocket has four, and fuel tanks, avionics , an upper stage, fairings, two solid rocket boosters ... ). An entire Falcon Heavy launch is <$100 million.
Any time now!
It's a very elegant idea, but maybe not the most empirically robust.