IIRC Musk said that Tesla was supposed to be the cash crop that eventually funds SpaceX.
Starlink, SpaceX's satellite constellation, is the cash crop.
Source is from the 2016 International Astronautical Congress talk in Mexico [1]:
> And I should say also that the main reason I'm personally accumulating assets is in order to fund this. So I really don't have any other motivation for personally accumulating assets, except to be able to make the biggest contribution I can to making life multiplanetary
[1] http://shitelonsays.com/transcript/making-humans-a-multiplan...