It is a great place to but stuff as long as it is something that can not be docked. I bought a few items are they were all docked which can be a real pain to get to. Now I only but stuff that can not be docked. I made some great profit by reselling stuff like shipyards and large ships. I also got Nova crystals way under market value which is like buying more money with less money.
What worse is, if you happen to own some stuffs you bought/bid from GM which are docked or shielded in ships/vehicles/stations or facilities/planets, if and the owner/s of those has/have been away for very long time to give you an entry access to them, or if the owner/s doesn't/don't give you the access due to security reason, you're pretty much screwed, like myself.
I also won the some Nova Crystal from GM Auction, which is stored in anti-grav sledder. Wanted to contact the owner, but since the owner wasn't willing to give an entry access to it, or if he/she had been away for long time due RL issue, there's nothing I can do but hope and get lucky.
Nova Crystals are one of the few assets that don't matter whether they're docked or not. Ownership is the value. Hell most of them are 'securely' locked away in Krath's whatever-vault.
But yes, the Public Market gets all kinds of goodies on it. I once bought a lightsabre belonging to a JO Grandmaster off the Market. Sure it was docked, and sure I really only bought it to return it at-cost to the JO, but that's a hell of a thing, no?
Just remember that the Market doesn't take your credits right away, so if you're bidding on a tonne of things, have care to when the auctions finish so you can ensure you've enough credits for when you need them.
FOr the NCs, only the ones on Kal`Shebbol in our vaults. Those that people have got possession of will only be exchanged if we have possession of it. I think the ones you are talking about were given free at the swapmeet where they then NPCed themselves.