Meh, not that big of a loss, they only go 600-650k anymore. People lose more that undercut by millions just to get an item sold faster.
Edit:
@Lakshmi.Naveyah
Damn that really sucks.
@Phoenix.Darki
500k is a loss yes, but not that big of a deal it's something you can recover from within a day or two of farming. A real loss would be like selling a KC for 550k or something.