Carl Sagan used to make that point. From a science perspective, you get a much, much better bang for your buck sending robots. But as Larry Niven pointed out to Sagan, every time you convince someone that manned space doesn't make sense you convince them there's no reason to go into space at all. Yes, NASA could do a lot more with its budget if it didn't do manned space, but if it didn't do manned space NASA might not exist at all.

  > every time you convince someone that manned space doesn't make sense you convince them there's no reason to go into space at all

That's just well-sounding nonsense. People can appreciate science and exploration even if it does not involve video of humans in outer space. Video or photos of celestial objects are enough reason for the laic public and there are many physical measurements that should be done to advance our knowledge. All this can be done very well and cheaper without humans onboard.

This mission's passengers appear to be funding it, at least in part.

In that case we're using the wrong word. Tourists go on "tours", not "missions".