For a tutor who is a native speaker, usually the cheapest possible is about 40,000won/hour. (The range is from about 40,000-70,000won/hour.) Also, just so you know, it is usually illegal for them to do that.

For a Korean English tutor, you can probably find one for about 20,000won/hour.

Usually, the more you spend, the better the quality of teacher. But there are some very good Korean tutors.

I work as an English teacher in Korea, and have lived in Korea over 4 years.