In what way is working an unpleasant job that you could choose not to do slavery? Sounds to me like the person prefers the probability of PTSD to the guarantee of a life of poverty. How is that not informed consent? Because we wouldn't choose the same when living in a life of not-poverty? Are we really reducing all people without a certain level of income to children who can no longer make decisions for themselves or enter into contractual arrangements?
That's actually one of the main arguments against paid blood/plasma donation, and the major reason that we don't pay for organ donations, because it results in a society where the poor literally sell their own health for basic survival. Plasma is sufficiently replenishable and donationations are safe enough that the net gain of lives saved is considered worth the societal risks.
Plasma, or other readily replenished fluids (there's another popular option, at least for men, though it carries other pregnant long-term implications) are propbably reasonably fair. There's little long-term harm or consequence.
A kidney, lung, or liver lobe, not so much.
Psychological research or DNA submission enters a pretty freighted grey area.
Pretty much. If your choice is either "Do X or live in poverty," what do you choose? Keep in mind that poverty is often a trap that is very difficult to get out of.
So basically if someone needs money, they cannot give consent because their judgment is clouded by their desperation?