I think the best bet is to publish a very limited version of your App for 99 cents, and then in the help file you can direct them to your website to upgrade to the full version.. this is fair enough to pay Google a little bit for advertising for you. 30 cents is not a big deal. Also keep in mind the many people trust Google with their credit cards than private websites even if the gateway is PayPal or your bank, so you might be losing some business as well.