There are several reason why your idea won't work, the least of which is that it's a terrible band-aid fix to a much bigger problem, and RMTs will easily circumvent your band-aid fixes. For my reason why it wouldnt work, (where I said that ppl can just put cheaper items for a LOT of gil and have the RMT buy it), you suggested putting a cap on each and every sellable item in the game. Who gets to make those decisions? What stops the player from putting up 99 ash logs being sold for 1000 gil each? How/when will SE adjust this cap during the eventual inflation of the game as the months pass?