They were able to reduce the network price from $70m/yr to $12m/yr [1] (their revenue was around $220m/yr btw).

There is almost no IPv6 yet since we still have enough IPv4 addresses. I am not sure how it is implemented but p2p has been often used in Korean services since 20 years ago.

[1]: https://m.businesspost.co.kr/BP?command=mobile_view&num=2986...