I'd personally pay $1 or $2 a month to be able to access something like an up-to-date, localized version of the Area Masters Guides, something with proper, detailed maps, bestiaries (type, level, aggressiveness), recipes and the like.

Yes, various wikis already cover the information, but the quality and quantity of coverage varies across different subjects across different wikis, and the best they can hope to do is duplicate information Square-Enix already has compiled internally anyway.