It was most likely all of the above reasons as to why he wasnt traded in combination with the low value he had at the deadline.
I disagree with several of your premises because yes I dont believe he had any "REAL" offers before that time. Very few teams were looking for a goalie at the deadline and even fewer had cap space still available to acquire him. Thats not even to mention the actual assets coming back which as Tallon has commented wasnt really worth considering. And I dont agree that it was illogical to say a deal wasnt made because a replacement was needed. To replace Vokoun, he wouldve had to give up something to do so...that had to be a valid factor into why Tallon didnt make a move as well. The net gain then on assets might not have been good enough to make a move.
Not to mention Vokoun was only willing to go to three specific teams.