A human presence on Mars might have the cost of "tons" of robots, but the results would be orders of magnitude greater in a shorter period of time.
Yeah, I get all that. And that's fine, as far as it goes. I wouldn't necessarily call it a publicity stunt. Though that kind of thing made more sense when we were competing with the USSR for hearts and minds and prestige. But it will be unbelievably expensive and has possibly and unacceptably high risk of death for the explorers. It's just too far for anything like our current technology. Isn't it like a 2 year mission? Given the kinds of safety testing and system redundancy we generally demand for our space program (especially after Challenger, etc.), there are just too many things that can go wrong that far away over that amount of time. When you are dealing with humans there is very low risk tolerance.
Believe me I want manned exploration and colonization of every rock in this system. Except Europa. Attempt no landing there...
In my opinion, if you really want to get serious about becoming a spacefaring civilization, you first concentrate on building the infrastructure to really drive things at scale. For the same cost, I bet we could get a permanent, full size space station capable enough to essentially be a shipyard in orbit for building larger interstellar ships; with enough left over for a permanent manned moon base.
Instead of one flashy Hail Mary mission to Mars, I'd rather set up permanent camp out in space instead of just visiting. That's much more feasible to set up locally first in our orbital space and nearest planetoid.
Unless gov money is unlimited, then do both.
But if Elon decides to spend his own cash to send himself, hey, rock on.