Okay ... half of experimental psychology papers are about giving people some small amount of money, or even just some token or just a chance to tell their story for filling out a questionnaire, sometimes extra credit is involved, or incarceration is involved (in psychiatric care) which is where I start having serious ethical problems with it.
Questionnaires where they reveal things, often associated with at least a way to contact them for an interview, but sometimes with name and everything, usually is psychiatric settings (where people are often incarcerated without any proof, trial or any of that I might add). Things like whether they stole from their employer. Whether they ever used violence to obtain sex. They often ask children, homeless, prisoners, patients ... other groups with perceived or real precarious situations. (things that would never pass an ethical review board for, say, medicine)
https://onlinelibrary.wiley.com/doi/abs/10.5694/j.1326-5377....
https://ajph.aphapublications.org/doi/full/10.2105/AJPH.91.1...
https://psycnet.apa.org/record/1991-07467-001
https://link.springer.com/article/10.1023/A:1020007004436
So yes, I would say that a lot of people are willing to give up a LOT more privacy than a face picture for a small reward.