This is partly why I'm skeptical of technologies when the media is talking about them. It probably means we're somewhere on the peak of inflated expectations.
The peak of inflated expectations was the Saturn V. Custom built, massive, cost around $10,000/lb in present day dollars to low earth orbit.
The trough of disillusionment was the Shuttle. Much smaller payload capacity, trapped in LEO so it ended manned deep space exploration, and cost around $50,000/lb to LEO.
The Falcon Heavy is the highest capacity launch system since the Saturn V, and will cost $1,000/lb to LEO. I think the plateau of productivity approaches.
Indeed - Elliott waves come in mind too. As un-scientific as those ideas can be, not being expressed in any kind of mathematics, they seem to point at some possible reality in growth patterns. Notably, the fact that there's always a plunge after a first surge - where everybody think it's dead and where it starts a new uptrend - is something that makes me really curious.
Note that it's not just about people expectation either : humans actually went on the moon, they didn't just talk about it, and they didn't go any further in decades. So beside expectation, it doesn't seem far fetched to say there indeed was a plunge in achievements, at least if we consider distance traveled by humans (which should grow again when/if we go on Mars).
This is partly why I'm skeptical of technologies when the media is talking about them. It probably means we're somewhere on the peak of inflated expectations.