Whereas people are making valid points about the flaws in this experiment, I don't think anyone at NASA thinks that this is a perfect dress rehearsal. It's about baby steps.
You can bring in the real-life high paid astronauts, build expensive underwater, or Himalayan bases, give them less sense of security, etc later.
If you think this is the only experiment that will happen you're mistaken, they're going to run similar tests numerous times. This experiment was about watching just basic psychology- start with a few factors, add some more, see the differences. See what causes the breaking point that would lead to a failed mission and try to alleviate it.
Many people here are programmers. You don't write an entire program in its entirety and then test it. You build chunks and test them as you go along. This was step one.