Well, I'm sure avex has their own base in China as well (I just searched, there is
www.avexchina.com, or to be more precise for ayu:
http://www.avexchina.com/artist_fxzp.asp?art_id=3). That means avexchina does release ayu's cd in China. The thing is there are too many bootlegs in China, so it is quite hard to judge which is official which is not.
But you're right on the quality issue. It is obvious that JPN version quality > HK/Taiwan/Singapore version > China version. Not only the JPN discs are made better, but the booklets are printed better as well.
It just depends on what you wanna get. Buying versions other than JPN version doesn't mean you dun support her. In the end she will get the profit
. Buying her JPN version cds means you can contribute to the sales in Oricon (if you buy it from the correct online cd stores, such as cdjapan... I'm not sure if yesasia's sales count in oricon).
For me, contribute sales to oricon is one of the reasons.. The most important thing is that I prefer a better quality cd
.