The reason why they are still in the exchange is because the price is nuts and no one is willing to buy them at those prices. This is why I usually see the prices as the upper bound on what people will actually pay.
By the way, I now have a mag regulator and all my weapons are anti-proton based. My advanced escort is ready for a dps showdown. My next big goal is to save up and equip a Sovereign class (so I can switch between attacking in my Prometheus and tanking in a Sovereign). I wonder if I can arrange my bridge officers so they'll function equally well on both ships.