you are a Red trusted member and seems has an issue of being a Liar , so how do we get the payment incase decided to join?

at least using Escrow would be great? 20 dollars for 50 people is 2k dollars and this can be best to escrow the funds for you to attract more participants.

I am not saying that you will scam people for 20 bucks but assurance is needed as there are many of these kind before that does not pay participants .