Just an idea.
What do you think if a campaign appears in which 16 people (or 100) will participate?
But only 1 user will receive the payment weekly. That is, by means of raffle, a winner will be determined who will receive the entire amount of the campaign’s weekly budget.
To my mind this kind of payment conditions would set the wrong incentives. If it is just a kind of raffle i guess you will attract those people who only fullfill the minimum requirements of participation while those who are far above will look for other campains.
To make it fair i guess you will need increased minimum requierements or some kind of winning chances related to effort by participants (quantity + quality). I am not a friend of the former while the latter seems to go against simplicity.