The books that have been on my wishlist for a while have been there for a very long time. It's obvious both that they're never going to get cheaper and that they're not worth it to me at the given price, to the extent that every now and then I go in and purge the oldest.
I have plenty to read and I'm lucky that overall I'm not invested in any particular author or series or topic; in the rare instances where I am, I just pay the going price.
ETA: Oops, I just saw this is the SF thread. I don't read SF, but I'll let my comment stand as I think it's a universal issue.