afaik, it's totally legal and lucrative for the J girls to work in Japan. In order to attract them to work overseas, the money has to be right. And the language barrior...
J and K girls are considered as exotics in China/HK/TW etc, the price is high due to the low supplies... if you want to compare to the locals, the going rate in HK is about $200 USD.
Oh, no need to mention the rate is even lower in Thailand and Vietnam.
see attached example from yesterday (in case you don't read Chinese, the posted rate was 1300HKD for covered service and 1500HKD for bbfs, BDSM 300 extra, swallow 200 extra)