There is a lot of "market shock" occuring with those older, previously pre-ban owners.
If you read some of the forums at AR15, there are a lot of guys who spent lot of money to own a pre-ban AR15. Now, the AWB is dead and the "pre-ban" status has vaporized like smoke. It's like they owned a rare rifle that is all of a sudden being imported in the thousands and has diluted the price since they are so available. There are many stories like this in this hobby. Buddy Hinton himself said he paid $1200 for a MAS 49/56 before they were imported in droves not long ago. For the same money two years ago, you could buy 4 of them will all of the accessories easily, including shipping for what Buddy paid for one rifle! So, the market is what really dictates the price of our collections.
Now, to the point you've made regarding the AR15 and pre-ban, I was lucky enough to contact anothe AR forum member and we worked an even-Steven swap---his suggestion, too. I send him my Eagle Arms/Armalite six month old reciever for his old, EA J15 pre-ban receiver. I live in a state that still has an AWB. He was happy to get a new receiver and I was thrilled to get a pre-ban so I could have all the bells and whistles. It was painless for both of us and it was a very fair trade, imho. Other posters there still feel that they should be able to demand extraordinary prices for their pre-bans since they paid extraordinary prices for them initially. The market rules, however, and if you poke around the forums and offer an attractive swap, you'll be able to find another collector who will be more than happy to execute a swap with you, too. I feel for those guys but the market is the market and just because you have a lot invested in something doesn't mean it's worth what you paid, especially when the market collapses around you. And, it also doesn't mean you HAVE to swap it out. Just don't expect everyone to have the same opinion. Keep what you have, in that case, and enjoy it.
Hope you find a swapping partner. I did and I'm a happy boy.
Rome