I agree. (Except for the estimate of cost - actual cost would be much higher IMO).
I'm a big supporter of our space programs - I think Hubble has been a wonderful investment for science and for the future of mankind. We've learned more from Hubble than the history of space study combined. I'm also for unmanned missions to planets and elsewhere to gather data.
But we've got far too many concerns to be spending that kind of cash on a mission that doesn't really pay off with discovery. I don't see what a man could do that a lander can't do - and there are other ways to invest in propulsion and logistics programs that may allow for the same discovery without the same investment that a manned mission to Mars would require.