Rubbish logic.
Just offer $100/blood bag, who do you think will come forward to "donate" their blood? The rich or poor? And if a poor donor does it 20 times over a year, he/she would have made $2,000. What's $100/bag to the rich? Too little that would bother the rich to come forward but a lot of money for the poor to "earn" with their blood to live. There'll be so many "poor" donors and the blood bank shelf space may have to expand.
Of course, there can be another bank that takes in free blood donation but for "poor" use only (for the "rich" to donate their blood to the poor..hehe). If a "rich" wants to use, pay to a sinking fund ...also only for "poor" use.
What's $100/bag to the "rich" to save his/her own live?
Blood-for-Cash essentially transfers money from the "rich" pocket to the "poor"
helping them in their financial difficulties while the life-saving blood helps to save the "rich".
Isn't that liang quan qi mei?