Baehu-Faehu in Windurst Waters (G-5) sells it for much cheaper than those on AH. Those doing Leathercraft can consider getting a few stacks from the NPC and stash it in your mule. 264 gil max from NPC is way much cheaper than buying from the AH.
Yes Evion they only come from regional vendors and the region in question is Sarutabaruta. 99.99% of the time windurst will control this so that is where you have to go to buy them for cheap. If you have airship access or otherwise have easy access to Windurst then it is worth it to buy them there and save the cash but if getting to Windurst is a pain you really might wanna cough up the extra 700 a stack to get them off AH. Think about it and weigh the options. Is it going to take you 45 minutes to get to Windy? You might as well just buy them off the AH. just my 2 gil anyway.
I walked all the way to San D'Oria Port to buy these things and he didn't have any. I think it might depend on which nation controls the area these come from...
