I used to donate plasma regularly back in the 1970s, for the money. I think I got 10 bucks a pop. The needle didn't freak me although I recall it was one bigass needle and left in for a long time! They had to draw the blood, put it through a centrifuge, and give you back your red and white blood cells and the rest of that glop. It felt cold going back in!
As I recall the most stringent protocols concerned making sure you got your own cells back and not somebody else's because if that somebody else had an incompatible blood type it would kill you! AND they wouldn't be able to do anything but watch you die!
I can't donate blood now because I take Finasteride. Before that I couldn’t because during the the early 80s I had gay sex a couple of times. By the time they lifted that restriction I had the prescription. My GP thinks the Finasteride exclusion is stupid but rules are rules.

My daughter worked for an outfit called OpenBiome that payed people $50 each--for turds! It was for fecal transplant. She told me the protocols were out the wazoo.