Exosomes Hair Growth Therapy - why are we lacking before and after photos?

I am hearing a lot of rumors about exosomes for hair thickening. I have read a few studies that showed success in converting hair from telogen to anagen phase in mice in vitro. A lot of hair treatment doctors are offering the treatment at exorbitant costs, however none of them are showing any extensive patient testimonials or before and after photos. How is this possible? How can something that costs $5000 per treatment not have extensive documented positive results?