$300! Wow. I pay about 80 from Comcast for the same service, actually unsure if it has a soft cap. We average about 600gb per month usage. Comcast is also our one and only choice so I am at their mercy with price changes.
https://digital-strategy.ec.europa.eu/en/library/mobile-and-...
Last time I lived in Seoul it was cheap there as well, but that was about 15 years ago.