"WHO PAYS?

A human mission to Mars could be surprisingly inexpensive. In the
1990s NASA produced a "Design Reference Mission" … just in case
they ever did get the funding. It estimated that a steady commitment of
$3 billion per year - about 20% of the current NASA budget and less
than 1% of the seemingly untouchable military budget - could send
three complete round-trip missions to the Red Planet within 15-20
years. The Mars Society claims a leaner, scaled-down mission could be
pulled off for half that amount. If we're going to spend $300-$400
billion per year forever until the end of time on "defense", can't we
spend a drop in the proverbial bucket for an undertaking worth
defending?"

...

"Our first human on Mars will be followed by the rest of her crew, and
then by more missions, and then by Mars Base Columbia, Mars Base
Challenger, Mars Base Soyuz, and Mars Base Apollo One. And these in
turn will be followed by the conquest of more planets, then by
colonies on Phobos and Deimos and Ganymede and Titan, and then - who knows, perhaps with someone 4 years old today as a 124-year-old
witness - by voyaging from our own solar system to another. De
profundis, ad planatae, ad astra - from the Earth to the planets to
the stars. "

Assuming the three round costs what is claimed. Then it seems the plan is to establish four bases (why 4, why not 12 or 1?). Then apparently NASA and the international community gallop off to colonize the rest of system. Why? Well, it seems they a unlimited tax payer funds to squander as they please. [Oh, what beautiful world we live in.] None of this makes any political or economical sense.
IF this "plan" was followed, what we would actually get is a few manned missions to Mars and once the "fun had gone out of it" we would get some kind of Apollo shutdown of the program. Leaving us with some relics on the Mars's surface and some memories of how wonderful and glorious is was. And to answer the question who pays, it appears that since most of the bases are American names, it will be Americans who are paying (and are paying a premium for the "joy" of dragging the "international partners" along [anyone notice France and Germany's behavior on the international stage?]).