IF you were to just transplant the area in that green you would not need more than 400 - 500 grafts. The reason you are getting variations in recommendations, is probably cause clinics know that reality is a lot different than pictures. You most likely have thinning in the front hairline as well, where you have existing hair and it would need transplanting. No one goes from thick hair to bald . It is a transition from thick hair to thinner and thinner hair and then bald. your pics show a clear bald skin that you want transplant but the "transition area" is left for the clinics to be interpreted.