The US approach to donation is odd, to say the least. You can't be paid for blood, or organs. Blood products, like plasma, aren't actually regulated and you can be compensated for them. The companies that collect those blood and organs you can't profit from? They can make money from those transactions.
Donating plasma and blood are different, yeah. My dad would donate plasma and was given a card that would be added to every time he went. I want to say it was like $50 each time, but you weren’t allowed to go too often.