How many marbles will that cost?

I have discovered a new reward system for good behavior and the job charts. I wanted to share with my fellow bloggers the basic idea because it is working really well (at least so far, the novelty hasn't worn off yet). My kiddos have a weekly job chart that includes things such as making beds, dishes, vacuuming, dusting, and simple things such as teeth brushing; they get a marble for each job that is checked off, plus I distribute extra marbles for extra jobs or nice things kids do. I have been know to had out a marble or two for doing a job the first time I ask or taking away marbles for not nice behavior or waiting till I am mad to finish a job. The kids collect their marbles in individual containers and enjoy watching them add up during the week. At the end of the week I add up all the marbles each child has and on Saturday night we have a reward party. So far we have had banana splits. They use their marbles to "buy" ice cream and toppings. Examples include 10 marbles for every scoop if ice cream, 8 for toppings such as hot fudge and caramel, 6 for whip cream, and 4 for a banana. For those small leftover marbles, they can be carried over till next week or purchase an M&M (two for one marble). The kids create their own sundaes using whatever amount of marbles they each earned. It has been fun so far. I am pondering non food rewards- maybe "paying" for TV time or WII time? I will have to see how this progresses. But I love finding systems that work. And bonus my kids are practicing their math skills.