I'm not sure what your first question has to do with what I'm saying...
And that's undoubtedly true about upside, but it sounds like there wasn't much upside in the package the Astros received in that deal.
I'm not sure what logic you "destroyed" once before, regarding how many prospects you need to compensate for a proven major leaguer. Or, as the case may be, two months of a proven major leaguer.
The best path to prosperity for the Nats is going to be to develop a strong core of in-house talent - draft, develop and promote, and then augment with select free agent fill-ins. When you have players who aren't a key part of the future - such as Hairston or Marquis - it's a good thing to deal them as the Nats did to get select prospects.
Ray would have rather the Nats just keep the two guys in hopes of eking out an extra win or two over the remainder of the season. To me, when it's obvious the team is "done" for the year, i.e. no longer in the running for even a distant wild card chance, then it's time to begin adjusting with the intent to improving the team in the next year(s).