After completing the registration process, candidates will be redirected to a new window to pay the application fee. The amount of application fee can be paid in online mode through credit/debit cards or net banking. 

Since the application fee for the last three years has not changed, therefore, it is expected to be the same as the previous year. Check the application fee of AIIMS MBBS 2019 and other info :

https://medicine.careers360.com/articles/aiims-mbbs-application-form