Maybe this actually part of a study to research whether having your research subjects pay you (rather than the other way around) has an effect the results of a study.
It's weird to ask people to pay to be part of a study. So maybe that is actually part of what this person is studying.
Maybe all the capsules are placebos and they are studying something else.
Can you tell I like conspiracy theories? :)
Oh I just noticed you are the person who posted this. You should do that, if this isn't what you're doing.