How much does everyone charge for private tutoring in maths?

To those who are doing private tutoring I'm just curious how much everyone charges for each tutorial and what your qualifications are. I know friends who don't even study maths at uni charging over $50 per hour (I guess it's justifiable since it's only high school level maths) while I see some people with PhDs in maths charging only around $20-30. I was wondering how much everyone charges or are willing to charge for tutorials.

(If it's okay I also want to know what people think is a reasonable amount to charge if I have a Bachelor's in maths and continuing to postgrad this year)

NOTE: This is NZ Dollars so in USD: 20 NZD = 11 USD and 50 NZD = 28 USD