A permanent Moon base would allow research opportunities that private LEO stations can't: ISRU, low gravity research, the far side of the Moon offers unique opportunities for astronomy (any spectrum), etc. pp. Long term, who knows what additional opportunities it opens up.
Falcon Heavy seems to have that capability though. I suspect that Starship will have similar cost to Falcon Heavy when they get done with it. Maybe marginally cheaper. The re-entry problem is really throwing a wrench into things.
For landing hovever it makes things signifficantly easier! You can break full arrival speed from lunar or interplanetary space (successfully done by Apollo missions) with a relatively light passive heatshield & land on parachutes. You can even brek to orbit instead or use the atmosphere to change incliunation of your orbit and other tricks (there are proposals for air breathing ion engines, etc.).
Lack of sufficient atmosphere is what makes landing on Mercury (no atmosphere, need to break to zero using rcoket thrust) and Mars (enough atmosphere to break from arrival speed, not enough to use parashutes or gliders for a soft landing) so difficult .
Even if by some miracle Starship carries people to Mars, there won't be anything for them to do there. They'll be stuck in their Starship and that would be the end of that mission, since there isn't even a plan to return.
If the planets are aligned the Delta-V is not that different between the two (Mars is about twice as much Delta-V for 100x the distance). You can use aerobraking in the Mars atmosphere but can do no such thing on the Moon. And then the last problem is that on the Moon you need to budget for a round trip, but on Mars we could produce fuel on the surface for the return trip. When you start thinking about all that it's obvious that Mars makes more sense.
Also, as far as I can tell from their last test video, they are still shredding their Flaperons at the joint.
https://spacenews.com/how-carrying-enough-water-to-make-retu...
https://spacenews.com/crewed-mars-missions-will-require-a-ne...
But I'm sure that approach also has drawbacks.
I'm sure SpaceX will eventually fix the problem. They are well funded, the materials exist, and they have amazing engineers. They just haven't reached that point yet.
Expensive compared to a 777 flight? Sure. Expensive compared to every other moon capable rocket? No.
They have set a hard goal, but they definitely have the expertise to make it work. I look forward to seeing the first orbital re-fueling.