It's not just the economical power of the regions. SE has a long history with German and French localization. It's way less of a hassle to work localization for regions you already have extensive experience.

Also I'm sorry but any additional language will never happen in FF XIV. The game has an insurmountable amount of text that would have to be localized and no brand in the entire world would be OK with releasing the localization "in parts". It's all or nothing, and just like English DQ X it will never be worth the cost.
Your only hope is for them to consider hiring spanish localizers for their next MMO if they make one.