I love the placebo effect, and think about it quite a bit, and try to use it on myself. My boss has been taking this herbal remedy for a month, to stop her migraines. Before, she "needed" some extra strong one a day pills to stop the migraines, now she just takes a placebo. I told her that it's a placebo, but not to think about it too much. She wasn't interested anyway, just said "well, it works for me!".
I have a really nice cheapo bass which was my first 6 string. I always thought I would invest in a really nice, more expensive bass when I could afford. When I could afford, I bought a very nice schecter, but, it doesn't play any better! For the first month I had it, I was raving on about how much better it was to play and how it was worth the money (it was though) etc, but, that was just the effect of having spent a lot of money on it. Once that effect wore off, I realised it just sounded a bit better, and looked nicer. Maybe a bit of the same effect with your basses?