Since these events do actively return every year, these items don't appreciate in price. About two years ago when I was actively playing it averaged at 250-300 DTs when DTs were roughly 7 pds each.
Once the event rolled around that time, it shot down from that price to 200 DTs. So a decent average back then, was about 250 DTs.
I'm sure it may still be around that range, or even less depending on how many dropped.
Seeing as there are less players I assume there are less floating around keeping the price range similar.
If anyone has any thoughts on this feel free to add on.
Good luck guys and Happy New Years