I'm guessing it may be targeting people with over 1,000,000 gil.

Most of these people are either Win sellers, who sell a win run for 500K and higher, and chest farmers, who have abused the current system to gather High value mats people pay high amount of gil for by joining groups and making people who want to run the dungeon leave so they can continue to harass another goup they will join to continue their chest farming.