Well, a focus on being able to get to Mars basically means "figure out how to launch stuff extremely cheaply". I think they've been clear that SpaceX is not going to build a Mars base, they just count on it happening once you've driven the cost for getting stuff to Mars sufficiently low. And if you can launch enough things into orbit that a Mars base is feasible, you'll certainly beat everyone else on commercial launches, too.

SpaceX plows all its profits into this goal. (Its shareholders aren't getting any returns, not for a long time. The SpaceX investors are playing an extremely long game.) And if you constantly use all your profits to improve your capability, you have a huge long-term advantage over companies that exist to make a profit for their shareholders.

"Figuring out how to launch stuff extremely cheaply" is not some kind of secret sauce or competitive strategy, it's literally what every rocket company is also working towards. The ability to specifically target Mars risks optimizing for a rocket that is extremely wasteful relative to what the market is willing to bear. Case in point, what companies want is not shipping material on Mars, the moon, or any deep space capability; they want satellites in Earth orbit. You don't need Starship for that, instead you need to double down on Falcon, and every dollar spent on the former is a dollar that's not spent on the latter.

Traditional aerospace is not -- ULA has shown zero incentive towards driving down launch costs, their interest is more in keeping prices up on their USG gravy launches.

Falcon is not fully reusable, there's a hard cost floor from the need to throw away a second stage for every launch, and there's no reasonable prospect to avoid doing so. The idea is that Starship will beat Falcon on launch costs long term. SpaceX itself is chomping at the bit getting Starlink to launch on Starship instead of Falcon, because it will be cheaper.