Has anyone noticed if the NPC venders in the guilds increase their inventories from PCs selling items to them?
I haven't really tested this myself, but I'm going to assume "No". This was something that SE did in FFXI. If you sold certain items (applicable to the guild), the NPC venders would later add those to their inventory or increase the amount available for sale. It didn't work with all items though. I just remember mainly the cooking and fishing guilds were good for this.
I don't like limiting one of my retainers to selling random bits (say for cooking) that I pick up from harvesting, would be nice to dump them on the proper guilds vender for others to purchase.