You can't set the list price any higher than anywhere else.
i. List Price. The “List Price” for an App is an amount that does not exceed, at any time, the lowest list price or suggested retail price for such App (including any similar edition, version or release) available or previously available on any Similar Service or the lowest actual price at which you make or made such App available for sale through any Similar Service. You will update the List Price for each App as necessary to ensure that it meets the requirements of this section 5i.
You could just differentiate your product by releasing the Amazon super version that includes some trivial feature not available in the Android market version. Clearly such a feature is worth doubling the list price.
i. List Price. The “List Price” for an App is an amount that does not exceed, at any time, the lowest list price or suggested retail price for such App (including any similar edition, version or release) available or previously available on any Similar Service or the lowest actual price at which you make or made such App available for sale through any Similar Service. You will update the List Price for each App as necessary to ensure that it meets the requirements of this section 5i.