Interesting discussion. I recently was talking about density with my surgeon the same topic. I've had a transplant with him and he's also checked for miniaturisation all over my scalp a couple of times to determine my pattern. Anyway he had some figures (based on his own experience) concerning density. He said someone with hispanic/mediterranean hair thick black hair can get away with 30% density - believe it or not - on a white scalp. That those with finer hair even if it's blonde on white skin, need 60% plus for respectable density. Huge difference. Of course you got to grow it out though.
Yeah, I think the key concept to accept when dealing with hair transplants is you are never going to be creating true density. The goal is the ILLUSION of density.
Surgeons all max out now at 50-60 units/cm2 for safe max transplantation. I find it hard to find data on the exact average "FU density" of natural hair but I found
this interesting surgeon's site. He lists some stats on some of his patients.
For example for
this hair transplant, the surgeon says it was:
Native density: 72, 93 and 88 FU/cm2 in temporal, parietal and occipital areas
Recipient density: 56 to 61 grafts/cm2
So if you have high native density of around 90 FU/cm2, and you get a 55 FU/cm2 "high density" transplant, you are left with only 61% of your natural density.
Can this create the illusion of natural hair? Perhaps. Is it the same as your natural hair? Obviously not by a long shot.
It's actually very disappointing to consider in many ways, as there is no conceivably way to improve this even with limitless donor supply. It simply has to do with incisions, blood flow, and scalp healing.