if these are cheaper than 400 in the AH buy them and sell them to the magic shop or outpost. these will go for 500-510 when selling them to NPC. Really common drop when training gudos for necklaces. Foe requiem sells for 60 gil to NPC and are also dropped can only carry one at a time, and often found in AH for 1-50gil.
A reason the people selling this scroll at the AH are doing it for cheap is so that low level mages can afford it. If you buy all of these just to make a little bit of quick gil you are actually raising the price of the item and making it unavailable for low level players.