The nominal compensation for plasma donors is for manufacture of a product category that is not for transplantation/transfusion. Even so, it skates close to the edge of acceptability as nominal compensation for time, inconvenience and discomfort, not for the donated plasma. This is the argument for nominal compensation for egg donors, too, that it's for their time and discomfort, not the egg(s). This thin legal fig leaf rises to be challenged from time to time when procurers make the valuable consideration valuable instead of nominal.
Marrow donors are not compensated, even nominally. A recent court decision distinguished peripheral blood stem cell donors as not marrow donors, and therefore not necessarily covered by the NOTA. This transplantable tissue is still regulated by the FDA, CDC, and the CBER, so nominal compensation for time and discomfort is the maximum allowed.
Propose an institutional framework of compensation with unambiguous professional financial incentives to improve the dignified treatment of donor candidates and donors, and remove the extant structures that incentivize volume over all, with neither true informed consent nor statistically valid long term longitudinal followup studies and care, and we have the merest beginning of a potential conversation. Without that minimal basis, you're singing the old song, and sellers are sellers, not donors.