You're reading too much into it. There's a difference in economies between servers on the same data center too. For example, Atomos' economy isn't as robust as others such as Tonberry so we see people coming to Atomos to buy but selling elsewhere. While that does benefit people on Atomos to a degree, the differences in the economies haven't equilibrated. If they opened up access to all servers to anyone around the world the various servers' economies would go bonkers and not settle down for a long time, if ever.
Opening up all JP servers to people on JP data centers and the same for NA and EU is reasonable. SE needs to be careful to maintain general parity in Relative Wealth across servers and regions.
You can be sure that SE NA/Europe are paying close attention to the economies in those regions and that information will influence the decision to open up cross-region travel or not.
To be completely frank, after getting fed up with the way Western/NA MMO communities behaved, I intentionally rolled on a JP server to avoid it. I don't want that BS making its way to the place I went to get away from it.
