Well there are more people that are willing to pay than just Coinbase. A more comprehensive answer would be that arbitrage is not that up to speed in the Bitcoin world, especially in KRW and JPY markets:
https://coinmarketcap.com/currencies/bitcoin/#markets
Used to be that crypto is massively overpriced there, now it looks like Korea and Japan are leading this price fall.
Used to be that crypto is massively overpriced there, now it looks like Korea and Japan are leading this price fall.