Your customers are not buying online SRS, they are buying an opportunity to improve their Chinese proficiency, and the experience of being the kind of person who wants to improve their Chinese proficiency. Never forget that.

I have a friend with an as-yet-unreleased application for studying Japanese. I told him what I'll tell you: I wouldn't consider charging less than $30 but I would consider trying more than $100. Yep, that is quite a range, and it all depends on what type of student you are targeting. To be perhaps a little unfair to my friends' prospective customers, I would expect to see no anime-related vocabulary in the $100+ product.

Exactly how you present your choice to the user is up to you. ($49 a semester, $80 if you buy a year at once should lead to an ARPU in excess of $100, hopefully.)