I’ve made some improvements in getting more conversions for my ad dollar: I now track them in a (marginally) more reliable fashion (I count them as converted when they open the page which automagically starts the download), I have discontinued some keywords which just weren’t generating results, and I’ve been continuously optimizing website design (observation #1: having a graphical button increases your visitor’s propensity to download by 100% versus having an understated text link).
This puts my conversion to trial download at approximately 15% for Google and 10% for Yahoo. This number varies wildly based on landing page/ad campaign: I convert at close to 40% for “make your own bingo card” and ~5% for generic elementary school teacher words (not unexpected). Also not unexpected: my cost per conversion is about a dollar.
At $1 per trial download, I need to convince 5% of buyers to pay up to make a profit at my price point. Thats, eh, possible I guess. We’ll see. Constant tweaking will continue.