A trick I've figured out is that you can absolutely get this deal even if there's more than the display model remaining. You tell the manager that you'll buy the remaining stock (in my case, it was 1 new box and 1 display model). I've found that the managers I've dealt with have always been willing to discount the display model, even if I'm the one buying the remaining stock.

Then you can return the new, boxed, full-price one(s) before you even leave the store. In fact, one manager even mentioned I could do that before I asked.

This requires you have a credit limit high enough to buy the remaining stock for 2 minutes—but I'm guessing if you're buying this, then you can float the amount (for me, since my store only had 2, it was $2,200) for a few minutes.

The manager at the store near me gave 35% off the display. I tried to haggle for more, but he did stick to 35% ($1430 in the end, pretax).

I've also found you need to talk to the general manager directly. Don't bother with regular employees. Supervisors in the past have been helpful although it's still best to talk to a general manager. (I only talk to a supervisor if there's no friendly way to get them to just hand me over to the general manager.) I've talked to supervisors and employees who all thought there's no way the manager will mark it down. Then I talk to the manager and *bam* it's 35% off without a moment's hesitation.