Charity auctions can raise more money with all-pay auctions than winner-pay auctions, but only when bidders have different levels of wealth. In situations where bidders know each other well, like in local clubs or show business events, winner-pay auctions can actually bring in more money. The study also looked at second-price all-pay auctions and found that setting minimum bids can make all-pay auctions more profitable than winner-pay auctions.