They would choose the flag based on the tax rate. However the tax rate is based on how many players use each and the one with the least has the best low tax rate. If the tax rate is lower, then you pay less for an item listed as the same price somewhere else. But not a lot of people care about it as the tax only pops up in the middle of buying it already and is for most things not much gil. On Cactuar, Limsa was the best a long time ago but now they are all about even.

Anyways I came here today looking for answers as to how someone on Cactuar has huge numbers of retainers and is selling Darksteel Ore, Gold Ore, and Spruce lumber, among other things, at around 300-400gil with 5-10 stacks of 99 and they reload multiple times a week. I figure either they have a ton of retainers and send them out every hour, or they'd have to be botting the nodes. But seriously we are talking 30+ retainers just for those, maybe like 100+ retainers in their empire. They all have names like Cactuar''''''one or Gerberbaby''''''two etc. Can they do that exploiting free accounts?

I mean it just kills gathering because they've moved in on all the reasonably high demand gathering mats that used to reliably have prices around 900-1000 gil each. Things are slow in the markets now which isn't all that surprising, but it's bad enough for crafters and gatherers as it is.