I've been a blood donor for most of my adult life, and have donated about 30 liters. Where I'm at you get a token donation and a thanks for donating, but someone mentioned that in the US you get paid quite a lot depending on the quality and the blood type.
I have a fairly uncommon blood type (about 10% of the population) and a blood count of around 150.
So, how wealthy would I have been if I had donated my blood in the US instead?
Where I am you get about 100 € tax write off per donation, one donation is about 0.5l so you could write off about 6 000 € from your personal tax returns.