Maybe you think it isn't going to happen - and sure there is some risk (!) - but in the successful case, SpaceX should be worth many trillions. At least.
If some follow-on vehicle were ever developed adequate to support a martian colony, and lunar gravity were to turn out to suffice, getting any actual value return from such a vehicle is hard to imagine. You might try to use it to support automated mining of platinum-group metals from asteroids, but it is far from clear how that could be made to work out. That it seems possible in principle is usually not considered a sound basis for investment.
Musk certainly understands all of the above. He will cash out long before it is demonstrated to all be a pipe dream.
How could any rocket that can deliver several tons be inadequate for that?
Pressure suits for everybody on board might be crammed in, but more likely just two or three to use collecting more from cargo ships already landed.
For that to make any sense at all, somebody would need to figure out a profitable economy for a Mars colony. Nobody has been able to do that.
Big defense contracts from the US military is where SpaceX will strike gold, if they do. All the money is in launching stuff into Earth orbit to serve some practical purpose on Earth.