I know that on my server (not saying which one because it will quickly change this) Scrolls of Sneak sell for 100-200 gil in the AH but 541 at the shop next to it in Widhurst Woods. I always nab those when I'm in the area.
I know there's a few things that you can get a profit off of from selling them to npc's (lizard tails, sneak scrolls) but is there anything else? I would like some other examples (and I'm sure others would too) to make a quick gil lol.