The private sector could pull it off
1. Sell seats on the Mission to Mars to the highest bidder
2. Pay per view only to watch the Mars landing
3. Reality TV show on the astronauts, their wives and bratty kids
4. Sell Mars Rocks on Home Shopping TV
5. Billboards and product placements
5. Naming rights for Mars cities
There is money to be made. I'm surprised private investment hasn't jumped all over this
I dont think those could generate enough money to fund a Mars Mission. Remember exploration in the age of sail was funded by the search for better routes to the east, which was the source of spice, silk, and other items. The economic drive allowed for exploration to be funded, because it was thought a shorter route would be more profitable.
Right now the reasources in space are not worth the effort to get to them. The real worth comes from the general pushing of scientifc discovery a project of this size generates.
Unfortunately the tangible benefits of this cannot be translated to an economic reason to invest in a Mars mission by a private group. The Return isn't there.
Space exploration, by which I mean cutting edge space exploration, is best controlled by the government. If we want to turn over satillite launches, and other earth orbit tasks to private industry I don't see an issue with that.