It’s so much worse than you realize. All blood and plasma must be obtained by “donation” for obvious ethical reasons, but American prisoners get incentives for participation/punishment for non-participation. Private American medical companies make billions of dollars in profit every year selling blood on the international market, but the prisoners don’t see a dime of it. The sellers are so unscrupulous that they have been caught knowingly selling tainted prisoner blood, and continuing to do so after being caught.

Yep! US allows plasma donation up to two times per week, with at least 48 hours between donations.

Can't donate plasma or blood for 8 weeks after donating whole blood, or 16 weeks after donating packed RBCs.

Packed RBCs are basically the reverse of plasma donation. Instead of returning the RBCs and keeping the plasma, they take two units of RBCs and return the plasma.