Felthove - two problems with getting many responses to your main question. First, a lot of the people on this site utilize the buy-used approach to trying things out, knowing that they can get out relatively cheaply if it doesn't work out. Hence, they don't have the financial incentive to "lie" to themselves. Second, if somebody does search for justification of an expensive, under-performing purchase, it may still be in progress.
I knowingly fall into the first category - can't tell you on the second. So far I've experimented a great deal, but rejected everything that cost any significant amount of money that didn't make a fairly large quality improvement. Since I've bought a lot of the equipment used, I just sell what didn't make a big enough difference to justify the cost and don't think twice about it.
Interesting question, though. I think your wine analogy shows that there are many areas where this question fits. I bought a floor-model Proton television set one time at a deep discount compared to it's list price, but not compared to a nice Toshiba or something. The picture struck me as great at the shop. Over the first month, I realized the picture was pretty horrible most of the time, but I had spent money impulsively and could have spent less and gotten more. It took me quite a while to admit to myself that it was a waste, get rid of it and get something decent. Such is life. -Kirk