The problem is not with Apple or iTunes but Avex. Back in January Apple gave in to the major music labels request to allow "variable pricing" (0.69, 0.99, 1.29) in exchange for them giving Apple DRM free high quality files. The downside however, is that not ALL labels, mainly the smaller ones or non-local ones like Avex, were part of this deal. Apple wants ALL songs in the store to be DRM free now and 256kbps AAC, but if the labels don't agree, then we as consumers are out of luck.
I just hope that they can make a deal soon and get Ayumi's stuff back on, in the new iTunes Plus format. What I would suggest you and everyone you know who can help, to do, is use the iTunes request page at
http://www.apple.com/feedback/itunes.html
We're gonna need to start pushing again so they realize there is enough interest!