LOL,
I used to always throw a codex into the army lot but everytime I did the customer would ask me not to send it for a reduced price on the army since they already had. Seems most tend to look at a codex prior to buying an army. Your mentality was the same as mine though.
As far as the high price I have found that I get more for the armies than when i messed around with regular auctions. If you do it as a regular auction you have to hope that there are 2 people who really want it bad so they drive the price up. Rarely does that happen. By using a higher buy it now and best offer you tend to get more for an army becuase the customer puts his max bid of what it's worth to him instead of trying to nudge by 1.00 by 1.00 in a regular auction.
Feel free to make offers guys.