10 Best Acell Matrix Hair Transplantation doctors in Greater Kailash Part 1

For a baldness level 2, where hair loss is relatively mild, the number of grafts needed may be lower compared to more advanced stages of baldness. Generally the cost is determined by the number of hair grafts required to cover the affected area.
You can go through our blog - Hair Transplant Surgery Cost in India

Hair transplant is one of the most effective and commonly chosen options for addressing baldness in the crown area of the scalp. Whether it is the right option for you depends on various factors, including your individual circumstances, preferences, and the extent of your hair loss. Talk to a hair transplant surgeon in your area. You can also opt for non-surgical options for managing hair loss in the crown area, such as medications or low-level laser therapy. 

40000 graft is a myth or may be wrongly heard. At max around 2500-3500 grafts can be implanted in one session and maximum 4000-4500 grafts may be implanted in two sessions. I have no idea about Chennai but surgery might take upto 6-8 hrs. and this varies from clinic to clinic.