The more I think about it, the more I think I would skip the free version and do $0.99 for the Hiragana and Katakana and then have the Kanji available in a price point similar to what you're doing now.

An example of this is http://www.amazon.com/Kanji-Pict-Graphix-Japanese-Mnemonics/... , which also offers the pocket size http://www.amazon.com/Kana-Pict-Graphix-Mnemonics-Japanese/d... . I've owned Kanji Pict-o-Graphix for almost a decade, but I also bought the cheaper, pocket size Kana Pict-o-Graphix for my brother-in-law (who hadn't studied Japanese before) before our trip to Japan.