I am a citizen of Korea, but I am sadly watching this phenomenon.
Then you already know the problem, for you to make a profit you will have to receive Bitcoins from abroad and then exchange them for fiat and send that back to your partner's country, but this is where the problems have always appeared for everyone trying to do this thing, you can't move large amounts between personal accounts without triggering controls and small amounts that would go below 1000 per transaction and 50k manually are simply not worth it.
The obvious clue that this will not work is that if it would have the price wouldn't be that different from other markets as arbitrage and a flood of coins would simply push them down. Besides, the exchanges would be the first to profit from this, but as you can see even they are not doing much about it.
We cannot be certain of yes, the price of Bitcoin is variable and a difference of 6-7% may occur within a short time, and therefore the faster your trading and on reliable platforms, the more guaranteed the profit, but less return.
The difference has always been there, it's not because of spikes or everything else, it's because of on of the strictest capital control in the world, and the thing only applies for the KRW part. For example, BTC/KWR is 71,637,000 which is around $61k, but the ETH/BTC pair is nearly the same as on Binance 0.0809 vs 0.0811.
The only opportunity would be in the KRW pairs but no way to take the profit out of the country.