Earlier quoted context omitted.
Blood banks do have plenty of real costs and a payment to the donator would just get passed through to the patients receiving the blood. It looks like I donate to a for profit organization, but for instance, the Red Cross isn't paying shareholders profits from the blood they sell.
Paying for blood, and the ethical issues around that, reminds me of pharmacies giving out gift cards and other discounts for flu shots. I recall CVS was giving out a $25 gift card to anyone who got a flu shot, and I imagined a lot of low income and poor people lining up for a shot they may not need, and in fact may be harmful, just to get money to buy food, etc.
That's an interesting spin, which may be true of other types of injection. However for flu shots, it can save lives (the poor are particularly susceptible and potentially focal for infection clusters). In that way the financial incentive is progressive.