That's about what I've been getting recently for my game. About 40% of the clicks from the ads result in downloads of the game, then about one out of 20 of the downloader's actually end up paying for a subscription. It seems getting people to click on ads and getting people to download (especially when it's a small download) are the relatively easy parts. Getting them to create an account once they've downloaded and getting them to pay once they've tried it are much harder.

30% is pretty amazing. I'm no expert, but if you google "click through rates" you get some good articles on the first page.

I think you're defiantly hitting your audience. You should try to get info on who's installing the app, and using it one week later, etc etc. if you can.

We're not actually getting 30% CTR in the google sense which is of 100 impressions of your ad, 30 clicked on it. That CTR is of the order of 1%. But of the 1% that reach our site 30% go on to download.