How often do the HE-400i's go on sale?

Been looking for a more detailed, portable alternative to the K7XX, and I think the new HE-400i with the 2.5mm connectors fits the bill.

I know it's gone on sale before for $300 at Amazon at least, but I haven't been in this hobby long enough to know the frequency with which this happens, and I wouldn't buy a pair at full price now for anything other than trying out. So, can anyone tell me when they might next go on sale?