Had a glance at the Zodiark MB and it's the same thing. The main sellers come from a few 6-9 person FC's (one is rank 8 on the server), consisting of a single crafter or two (always with 1 lv80 DoW class, maxed DoH/L and only the story minion/mounts) and a set of low level retainer classes using jobs that start in Limsa for easy MB access. One of them originates from Lich, so they use trades to retainer alts on multiple worlds to cover the entire data centre. It's rampant and quite a few Neo-Ishgard pieces are below material price.

This first started happening on a large scale around 4.5 onwards, when endgame gear crafting was made much easier and cross world was implemented. Both these changes created a bot heaven, simple crafts, easy to obtain mats and the entire data centre as your market. It's a shame.