I would not personally be motivated to donate a kidney (as a living donor) for research, nor would I be enthusiastic about a foundation to do that. My enthusiasm for living kidney donation is completely related to the benefit to another person, weighed against the risk/cost to the donor. I happen to agree with the founders of the 1DaySooner organization, one of whom (the main person, IIRC) is a living kidney donor who is motivated by what she sees as a clear moral equivalency between living kidney donation and the challenge trial.
Your comments about the profits potentially earned by companies don’t seem relevant here, since that applies regardless of how a trial is organized.
Perhaps you mean to call concerned attention to the size of compensation of volunteers. I agree that this is a concern that should be part of ethical considerations.