That’s core to their strategy. They also assembled a lot of the rocket in tents on a beach in Texas.
Originally they hired a company that normally builds water towers to construct it. The idea is that the rocket needs to be a commodity, not something built in a clean room by specialists.
I almost wonder if this is one of the key differences related to development speed between SpaceX and their competitors (Blue Origin, etc.) Most big space rockets are built in relatively low unit counts as ordered (unless I'm mistaken), whereas Musk's other large concern focuses on mass-production and solves problems for mass production. Hearing Musk speak about manufacturing challenges in the Everyday Astronaut interview, much of what he was talking about in terms of manufacturing challenge was about lessons learned from Tesla. Seems like focusing on the production problems this way may be a reason he's pulling of launch vehicles at the price points SpaceX is achieving.
For sure, it also has to do with vertical integration. If you don't have that, then you need to ask every one of your suppliers to take the approach you do.
In a risky venture this is very hard to achieve.
SpaceX can just say 'we are gone do it this way' and they have almost everything required in house and can plan for mass manufacture from the beginning.
Originally they hired a company that normally builds water towers to construct it. The idea is that the rocket needs to be a commodity, not something built in a clean room by specialists.