Your timing is not great. The price of guns in general is down since the last election and right now the .40 is an unpopular caliber. I have been able to pick up bulk ammo for less than the price of 9mm and have gotten some real deals on guns. I still like the caliber but a lot of people are dumping it. I have no interest in shooting it in a small gun like a Kahr MK, though. From what I see, clean K40 and MK40 pistols, even including elites, sell ok for $350 - $400 and maybe up to about $425, but over that may sit for a while. There are regional differences. An MK9 is worth more than an MK40 at the moment.

Just my opinion. of course and I hope you can do much better. I can't recall for sure but I think the MK40 frame is the same as the MK9. If so, you might want to sell the grips separately.