1. Well, registration fees or stamp duty varies in every state and there is no uniformity in such rate in all over India.
2. So you can take local lawyer to verify the authenticity in the demand made by the registrar.
3. Apparently no such clause exists as if the POA is not made within blood relations then it is not valid as per decision of the Supreme Court in Sooraj lamp case.
4. So I suggest you to engage a local lawyer to verify the demand of the Registrar.