I think this is an example of the "post hoc" fallacy. Because of the fact that we went to the moon in a certain way successfully, and no other programs have done so in the intervening time we end up with this idea that the Apollo project was the only way to do it.

And, to be fair, Apollo may have been the only way to do it so quickly. But let's look at some fundamentals. Why is spaceflight so expensive? The rocket equation is brutally exponential, for sure, especially up in the delta-V ranges needed to get to orbit. And yet the cost of fuel and materials does not explain the cost of spaceflight, those are tiny fractions of the cost of a single launch, in the 1% or less range. Instead, the cost is much more tied up with operational complexity, manufacturing scale and complexity, and so forth. When you produce custom vehicles in low quantities and each of them are one use, things can get expensive quickly.

But a big part of the reason why launch has been expensive has been due to the fact that it has been a government project for decades. Governments are not known for their cost efficiencies, and that has certainly shown through in spaceflight. The typical top-down, decade long or longer, multi-billion dollar project approach to spaceflight has certainly seen a lot of ups and downs over the last few decades, but it has done almost nothing to make spaceflight cheaper or more easily available. And yet look at what happens when commercial enterprise is let loose on the problem, SpaceX being the best example of course, but hardly the only example.

So many people think that the way to dramatically lower the cost of spaceflight is through some revolutionary means. New materials. New types of rocket engines. New designs. And so forth. None of this is true. What is needed is merely iteration. Practice. Persistence and pragmatism. Nothing more.

And shockingly, such things have not been tried very much in launch vehicle design or manufacture in the many decades since humans have been building orbital rockets. SpaceX's rockets are hardly revolutionary, they are merely pragmatic. But their iteration cycle time is now down to only a few years, and they are already working on building their 4th and 5th generation rockets in their short history, and in so doing dropping the cost floor out of the rocket business lower and lower with every step.

Now imagine for a moment if instead of doing Apollo, and Skylab, and the Shuttle, and ISS (projects totaling up a good chunk of a trillion dollars in expenditures) only a fraction of that amount of money had been spent working diligently (with pragmatism and persistence) on improving rocket designs year by year, decade by decade. Imagine if many of the greatest engineering minds of the Cold War generation had been working not in the service of their country to achieve a goal no matter the expense but to produce clever and innovative designs to lower the cost of access to space.

I have no doubt in my mind that they would have succeeded at least to the same degree as the SpaceX Falcon 9 has. Such a rocket is a simple design, it's just a two stage LOX/Kerosene launcher made mostly out of aluminum parts. Certainly the engineers of an earlier era would not have had the benefit of friction stir welding, CFD simulations, and so forth, but they would have been able to achieve quite a lot. And with economies of scale in manufacturing vehicles in an assembly line they would have produced fairly decent cost levels as well.

And then what happens when you take NASA's budget from any year after the Apollo program's heyday and you apply that to the ability not merely to launch a paltry half dozen or so Shuttles a year but to put up a station like the ISS and launch over a hundred astronauts, and more. Every. Year. And I'm not exaggerating, these are fairly conservative estimates and I've taken into account the overhead of developing hardware and astronaut operations and so forth. That's just how much farther money can go when there are systems in place which have been designed from the ground up with cost in mind.

Then ask yourself. If so much could be done in a single year with nothing more than a run-of-the-mill historical NASA budget, then what happens over decades? If by 1970, 1980, or even 1990 it had become possible to achieve such launch costs, what would we see today? I'll tell you. We wouldn't just have gone to the Moon, we would have stayed. There would be cities in orbit, and outposts on Mars by now.