Over the span of little over a decade, SpaceX went from being a space company made up of amateur rocketeers and a dude who helped start an internet banking company to our best chance to set up a colony on Mars. Along the way, it's managed to create the cheapest rockets we've seen yet.

Now, when SpaceX says it can launch a military rocket for $90 million compared to ULA's $380 million, you just kind of nod your head and move on.

The reasons the company can offer launches for a quarter the price of competitors are often contained in a throwaway line in an article somewhere: The company does most everything in-house and have little of the bloat common in rocketry today. That quick explanation isn't inaccurate, but it's a little bit flip.

What does it actually mean to make everything in house? And how does the company do it so much cheaper than everyone else?

SpaceX will load a rocket with both the legacy part and the one it's designed in house, and test them both without making a big deal out of it

SpaceX has been an utterly fascinating story to follow—its attempts to land a rocket on a barge in the middle of the ocean actually get my heart racing—but rarely do we get a look at what goes on inside its factory in Hawthorne, California.