But you can't beat actually being there. Would you rather a trip to Europe or sit and watch a documentary...or see the video from someone else's trip.
When it comes to the expenditure, you can always spend the money on "something better" (feed the starving, world peace, alternate energy research etc). I am sure when Columbus, Cook and others set out, there were other things where the money could be better spent...but they still went (I think they would have still gone even if they had robots).
If they needed volunteers to sit in a space ship for a year and travel to Mars, stay a few months and come back...I would do it! I can always play Solitaire on the computer, it would be just like being at work....oops...who said that?
Why should robots have all the fun!