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?