The only required cost of our service is the app license which may be purchased directly from https://gonative.io/pricing.
In addition to the app license, we offer a variety of premium add-ons and services. We are also happy to provide a "full-service" solution, where our team handles everything for you until your apps are published and available in the app stores. More info at https://gonative.io/pricing.
The only requirement is that your website is mobile-friendly. We can provide custom native development for an additional fee, though often any desired changes may be applied directly to your website so that they will work in both your website and your apps with no additional native development required.
Please see some examples of recently published apps at https://gonative.io/examples.