While they have about $16 billion in Model 3 orders. So to actually sell so many cars, they need to invest a lot to get the production going. Part of that is the Gigafactory, but also the production line and of course, the parts for those cars have to be bought, before the cars can be made and sold. So the next quarters will see a lot of more spending that has to be balanced with the future Model 3 revenue.

The SolarCity acquisition is certainly risky, but there are large business overlaps as other posters have described.