Taekwondo childrens class?

My son (age 5) has just had an introductory class (which he loved) however I have been told it will cost �35 a month (includes uniform though) for a 45 min weekly session. There will also be an additional �25 (every 2/3 months for grading) I was wondering whether this was a fair price as I have never had any martial arts training and so have no idea what to expect, I only work part time so its seems a lot but would pay it if reasonable as son is sooooo excited