In order for your application to be accepted, you must pay a visa fee when you attend the interview. In most cases, a long-term family reunion visa (category D) costs 75,00 Euros for adults and 37,50 Euros for children under the age of 18.
You will not be entitled to get your money back if you plan to cancel your application after paying the fee. You will also not be reimbursed if your visa application is denied. You will have to pay the fee again if you wish to reapply for a Germany family reunification visa.