SpaceX is ramping up there production. In October they produced there 100th Merlin motor eventually they will produce 40 rocket cores annually.
Having 2 tanks in the first stage, two tanks in the second stage.
Having nine Merlin motors on the first stage and one on the seconds stage.
That adds up to:
Amount of tanks: 4 x 40 = 120 tanks annually.
Amount of motors 10 x 40 + 400 motors annually
It is clear that SpaceX is growing rapidly to become one of the biggest private launch suppliers.
It’s worth to watch this video repeatedly and concentrate on a one place in the production process. You will notice that there is a lot going on, like the welding of the tank elements in the white tent on the left.