Sales regarding

Hi All,
I have created an item one month ago and pushed 5 updates in single month too. I am dedicated for support too, generally reply in 1-2 hours. Unfortunately, my sales are very low, I don’t no why ? All comments are positive. Received two reviews with very good feedback,

Please guide me , item url is http://codecanyon.net/item/express-invoice-with-stock-account-solutions/15467114
When I compare similar item with less features, all have better sale then my item.

Thanks