Gil sellers don't typically flip items on the market board with their gil, though. They sell it for RL cash. It seems way more likely that it's a player with a large amount of gil trying to corner a market by reselling the leathers at a profit.
In any case, bots farming T4 doesn't seem very likely to me. Have you ever seen a tank bot in a dungeon? All they do is autoattack one mob at a time. They can't hold hate worth half a crap and they don't use defensive cooldowns; they just stand there and die. Outdated though the content may be, Dreadnaughts still hit friggin hard. They can one-shot anything other than a tank (and could probably even one-shot a poorly geared tank), so even if they have healers spam healing the tanks, all that ends in is two dead healers and the rest of the party soon following. Seriously, just farm some T4 yourself if you need the leathers. It's a 5 minute run at most.
Why should they pass? Zodiac relics take 80k seals. Lucis tools take 80k seals apiece as well.
Or maybe they're desynthing them too.
