Q:
Weird item prices on the tp
A:
It was actually confirmed by Anet that RMT do launder gold that way a month or two ago when they accidentally flagged the one player selling the old rabbit PvP boxes. Well I think it was those that he was selling.
in a lot of cases, money laundering for RMT
I doubt they do, but the people buying for lower prices are probably flippers using an api to tell them what to buy to make the most money and due to the variance in buy/sell prices they order in order to flip. and make the largest profit margin.
What about this? 15s buy order for a masterwork earring. You can craft it from 8s. Also he is buying huge amount multiple times.
https://www.gw2bltc.com/en/item/13442-Chrysocola-Mithril-Earring
Same happened with the ring, but it seems he likes earrings now.