It's not easy. It's damned difficult and we both know it. But effort "funnels down" into conceptually simple results even more often in non-software engineering. It has to, or physical engineers would never get anything done. Choices like fuel/oxidizer composition, stage design, and nozzle type can be (relatively) easily specified no matter how much trouble went into deciding between alternatives. Pages of physics calculations and days of simulation bake down into a few numerical parameters in the final design.

I think what's happening here is that you know and respect the amount of effort that goes into rocketry and your mind is inferring a level of complexity that matches. Effort(times)skill is one correct way to judge the magnitude of a project, but I argue that complexity of the product bears little relation to either effort(times)skill or the project's success.

Rocketry was a bad example because the scale of a typical rocketry project is so large that dividing by cost (or effort(times)skill) becomes critical to making the comparison.