This late in the ladder you probably did well to get just 5 fg for them. For the first couple of months in a ladder they're in more demand but this late, with a reset 2 months away, there aren't many buyers for much of anything.
While they're in demand, perfect amethysts go for 1/2 or 1 fg each from traders who roll crafted ammy's. Rubies sometimes get that much as well. If you had a mix of pgems a couple of months ago, for 40 you might have gotten 10 or even 15 fg. But a month ago I had a batch of 80 to sell, and didn't get any offers.