I think that you have a great product and I myself would be happy to pay for the addition of Push Notification, but at present your Application Description in the iTunes Store is very misleading.
You advertise the Push Notification ability as a new feature in your Application Description on the App Store without stating that there is an additional cost to activate it. New customers would not find this out until after the purchase, and I believe you might be liable if they decide to take action.
Also, if you are still waiting for approval, then maybe it would be wise not to advertise it as a new feature just yet.
Nobody would want you to have go out of business for this oversight, so I hope you update your site before it generates a lot of negative repercussions.