Crypto arbitrage globally

Hi guys, I noticed something really interesting today my friend in India sent me some BTC and when I checked the amount its was around $100 less than what he was supposed to send. I then checked the rates of the exchange he used and it seems almost every major exchange in India has a good difference in their prices not only in BTC but all the other cryptos.. So now my question became why hasn’t anyone taken advantage of this opportunity.. i know the margin isn’t really great you would make something closer to $1200-1500 on 1 BTC but it definitely made me curious as to someone doing this on a big scale and profiting..

Would love to hear the communities thoughts!