This isn’t really an answer to the questions posed, but it brings to mind a realization that I had a couple of years ago; namely, that my definition of “bargain” has changed.
There was a time when I would consider a gun a “bargain” if it was priced below what I thought was “market value.”
As my collecting interest have gotten more specific—and the holes in my modest collection have become more difficult to fill—I now consider a gun a “bargain” if I find a gun I *really* want that is for sale at a price I can afford.
For example, if I were to come across a Registered Magnum for $2K it wouldn’t be a “bargain” for me, as I’m not particularly interested in such things. OTOH, if I were to find a nice Airweight Centennial from 1953 at that price I might break out in a happy dance.
But back to the original questions, I don’t think there is any secret to finding bargains apart from patience, keeping one’s eyes open, and having cash on-hand to pounce when the opportunity presents itself.