There WILL be price difference in every country even if they have many algorithm trading system that promises arbitrage.
Like I have said, I was in FX, Future, Options, Stocks... So I have seen many.
I think it will work since the market demand (aka human greed) will move each country's market price separately.
If there's 1% difference, you can make money. And if there are no difference between two countries, there will be another country with good price.
It will move. It always did.
I am just trying to be realistic. not just having hopes.