One reason is JL has a ticket service fee on top of any other fees the ticket normally has. I want to say it's about $40. I think another reason is that their overseas phone lines are notoriously difficult to reach and their number in Japan is not toll-free (free dial). If you're actually in Tokyo and can go in person to the Yurakucho service center then it would be ok, but knowing how much time these tickets can take to issue and adjust later, you could rack up quite a charge to call the Tokyo number to get good agents. (Last time I called the US number it was a call center in the Philippines and more in depth knowledge was limited)