First, let us say that these ideas are just that, ideas. Several teachers have tried things like this and with input from other teachers in our group came up with the idea presented below.
To teach students the "value" of a full day's work. Bring in a few items to auction off or sell(candy, pencils, folders, etc.). Tell students that you are going to pay them for the work they have done in class. Before class, total up all their points for the current six weeks or previous six weeks (4 points per A, 3 points per B, and so on) Then pay them one dollar per point (play money, of course). The harder they worked the more they make - just like the real world sometimes.
Once paid, they can now buy or bid on the items you have to offer. There should be a bidding war and inflation on items as you begin to run out of them.
This should create some economic interest in class and students will want to do it again and again.
If you use this ideas please email me and let me know what you did and how it worked so that I can pass that information along to other teachers.