Somehow SE manages to be so special that they can't figure out how to implement additional storage space without it costing them an arm and a leg - even though pretty much every MMO out there can do this.

Or they saw they have a fanatically loyal fanbase and knew they could get them to pay unnecessary additional money even though technically it would barely cost SE anything.

I doubt we'll ever see additional inventory expansion in XIV without having to pay additional money for it - not with this precedent now set. It's ridiculous in a sub-based MMO, but too many people just roll over and let it happen.