Ishgard, Taxes & the Nearing of 3.1

[Apocrypher]

pretty sure they can just look at the database for a tally of everyone's gil instead of having to resort to using tax to determine it. lol

Actually, the marketboard system was most likely first implemented as to keep tabs on the frequency & amount of gil trading hands in addition to more blatantly being a small gil-sink measure to curb the volume of gil per server. Due to the 1-million gil per transfer limitation on face-to-face trades & in-game mail, the marketboard is a more widely-used system and therefore provides a more in-depth screenshot of a server's economic status at any given time because people are more likely use its higher convenience level than the tediousness of trading/mailing (especially in the game of big-name items).