For CA Inter & Final Costing you must go with Purushottam Agarwal Sir because he is the best faculty for this subject and he cover 100% Institute materials.
teaching technique is also exam oriented and sir provides many short tricks which will help you in exam. Also the best thing i liked about sir is points to remember which helps in revising in exam time.
Sankalp kanstiya is worst teacher for costing. his teaching is not upto mark for ca final . many concepts were not a t all covered in his classes and poor explanation of some topics. i also bought his classes but now i am doing with self study. his many agents are active in social media who will suggest he is best teacher but trust me beware of such fraud teachers.