Ask HN: Pricing: How would you price Code Pal?

Our product is Code Pal: http://www.codepal.me

It is a way to learn programming in a fun and engaging way. Basically, we allow students to learn programming by using their own social data (imagine writing a for loop to print out the names of all your Facebook friends etc.). Our target market is students (and potentially teachers who want to use it in their class).

My question is how do you price the product? Right now, I allow students to try out 10 exercises for FREE and then charge $29.95 to access the remaining ones. I am not sure what to benchmark the price against. Charging too much is clearly not going to work but how much is too much. Also, I don't have enough traffic at this time to A/B test pricing.

How should we proceed?