Usually when there are big differences between exchanges, arbitrage will cause them to move towards each other in price. (I'm going to ignore Russia here because Russia has obvious reasons to lag behind).
Now the European and American exchanges haven't really moved much today but China actually went up to 2123 ($336 or €305.5)
Why is China so much more expensive? Are we just slow to respond? Does China have good reasons to be more expensive?
Depending on how hard it is to trade in Chinese accounts it seems like free money, buy Bitcoin in an European or American exchange, move the Bitcoin to a Chinese exchange, sell it for CNY, sell the CNY for dollars/euros, buy Bitcoin for those, rinse and repeat.
This might be harder than it sounds.
The only reasonable answer it will be because there are to much demand. Chineses want to have bitcoin and bitcoin is seeing a good situation there. This demand cannot be satisfied by the supply. The Chinese miners have not enough bitcoin to satisfy the need of the market for those. The others who have bitcoins don't prefer to sell. So the price go higher and is higher even than in the other exchanges. This can happen even maybe the Chinese exchanges are not connected to much with the other important world exchanges. This cannot allow "the game" between various exchangers (buy at the exchange where and when the price is low and sell at the Chinese one where the price is high). At least this is my explanation.