I got the idea from a friend, who also is very creative in Children's Ministry. I usually fit 4 or 5 bills on a sheet of paper. Kids can earn bucks by sitting quietly, cheering, doing actions, answering questions correctly, or any other way I can think of. Kids save their Wise Buy Bucks until the end of the month, when we open the Wise Buy Buck Store. This is a large sheet of plywood with prizes stapled to it.
Different toys have different values.
Our lowest priced item costs 3 Wise Buy Bucks, and our highest is 10. Kids learn to save their money, and how to spend it wisely. We not only have toys at the store, buy also practical items like Children's Bibles, Books, Mittens, etc. I make a Tree shape using poster board, or coragated paper and put it overtop of a sheet of styrophome. Then I poke tons of holes everywhere.