How much is a 1988 printers proof Wheaties box worth.?

I have a 1988 printers proof Wheaties box in mint condition. This is a unique item because it is the box had the Denver Broncos won. They lost in a blow out that year to the Washington Redskins. I'm guessing very few of these exist. I would like to know a ruff estimate of its value. I plan to sell this item on e-bay or at a convention. I need some moving money. Thanks for your help.