* Buy BTC with USD outside China
  * Sell the BTC in China for RMB
  * Use the RMB to buy goods or stock in Chinese market
  * Sell goods/stock outside China for USD

Would this work:

  * Buy BTC with USD outside China
  * Sell the BTC in China for RMB
  * Use the RMB to buy goods or stock in Chinese market
  * Sell goods/stock outside China for USD

or the other way around.   Not for amateurs, of course.

This would equalize prices but according to some "exchange rate" that is not the official one, due to extra costs.

Which is what we see, right? They track each other but not at the official exchange rate.

Wait please.  I missed it among the trash.  Cliff's notes version please.

The opposite direction involves buying BTC with RMB which is challenging right now.

If you have deep pockets you do not need to transfer funds right before/after each purchase.  You start with a large pile of USD (or RMB) and end with a large pile of RMB (or USD) that is worth more than what you started with, even though it may take months or years to get it out (or in).

For example, as of yesterday it would seem that pocketing one USD in Japan (that's where Mt Gox is?) is as good as pocketing 5.3 CNY in China, even though the official exchange rate is 6.07 or so.