Everyone is different! I may be fortunate with a good donor, but I am a NW5 diffuse so I will need quite a lot of grafts for full coverage.
65-75 is very decent in terms of density, most people have a graft to hair ratio of 2.05-2.25 so assuming you're in that range you're looking at 140 to 160 hairs per cm^2.
Remember other characteristics are equally as important to help with the illusion of density, such as as hair color, scalp/skin color, and of course hair thickness. Someone with thick hair but a bad skin/hair contrast will need more grafts vs someone with a white or pale skin and light blonde hair.