A brief FYI..... Selling your plasma is a good deed. But it isn't a blood donation. Plasma is just one of the components of blood. Probably the most widely used component. Some people can have plasma drawn twice a week (note to those who do this - be careful. There are vein scarring risks). Other major components are red blood cells, white blood cells, platelets, and cryoprecipitated antihemophilic factor (AHF)
Whole blood (the non-plasma components) is more difficult to screen for disease and doesn't store as well, or for as long as plasma. Perfect market conditions would make it that you could get paid more for your blood than for your plasma. However, the FDA regulates this, and it's too involved to explain why here, the US blood supply relies on donated blood. You can only donate blood every 8 weeks.
Please donate your blood. It's a great thing to do.
Lastly - I'm no authority. I have some interest in this and have done some reading. Take it for what it is - just an attempt to clarify.