I don't believe that a manned mission to mars could ever be achieved from international competition. It would require international cooperation on a massive scale.
Costly, expensive does not even begin to cover it. A program for a manned mission to Mars is at least a magnitude of order more difficult than the Apollo program. A starting guess would be 10x of the cost of the Apollo program in adjusted dollars for inflation. One figure I found was $135-billion in 2005 Dollars (cost of the Apollo program).
Now if it is 10x harder to do mars, are we talking about 1.3 Trillion?
Personally I would like to see this seriously pursued in my lifetime, however ..
We have gotten good at robotic missions and I would like to see more exploration and science missions. I know that a sample return mission would get some level of excitement, but it is likely that placing more science on the surface is of more benefit. Maybe rovers with an ability to find samples to be sent to a surface based robotic lab instead of / in addition to of self contained rovers.
We also must ask if Mars is to use so many resources would we be neglecting other robotic planetary missions?