As I understand it, the application is using Apple's APIs which could include things Apple needs to pay license fees to other parties for.
If not, I wouldn't be opposed to the paying to review apps outside of the App Store (where their 30% cut assumedly takes into account for App store apps), as long as the review is purely for security and not to comply with App Store rules (since I am not hosting it on the app store). But charging everytime someone download a semi-popular app, or worse, updates that app (since the install fee is per year) starts to go beyond "what value am I bringing to this feature?"