It's as expensive as it is (at least at the current time) utterly pointless. We can conduct the same science that any manned mission would do for 1/100 the cost, 10x better and faster, using robotic probes.
Perhaps but there will then come a time were we might have to leave this planet, and i for one hope we have some trained people to get us moving. As well as populations on the moon. 1 asteroid can ruin our whole day.
In terms of objectives related to science, that is true.
If we are to pursue "Space Manifest Destiny" goals (space colonization, etc.) basic technology will have to advance a few more steps to enable space resource processing at cost-effective levels.
The von Braun paradigm of space exploration is about to collapse under its own weight, IMO.
Right there is a problem. It is not necessary to do any more science in space at all, if indeed any science has yet been done in space. Repeal the Treaty and get the Socialists out of our way.