But even if they are willing to pay a premium, at a $100 spread there should be a lot of traders willing to jump into the market which would close the gap, unle

But even if they are willing to pay a premium, at a $100 spread there should be a lot of traders willing to jump into the market which would close the gap, unless they are prevented from doing so. If there are capital controls they are surely on USD not BTC, so if anything USD should be more valuable within China.