I would have guessed that the reason for prohibiting payment for blood would be the same as the reason prohibiting payment for organ donations. Interesting that in this case it is blamed on trying to minimize donations from people with HIV.
If I give $350 in cash to the American Red Cross, I can take that charitable deduction from my annual filing. If I donate a unit of blood that gives ARC $350 in products, that's not deductible.
The incentive side steps the donor-with-marginal-income problem, unless I'm missing something.
Not Deductible As Charitable Contributions:
Cost of raffle, bingo, or lottery tickets
Dues, fees, or bills paid to ...
Tuition
Value of your time or services
*Value of blood given to a blood bank*
It's amazing how many details the IRS pubs cover. I like your proposal though.