You are presented with three non-car prizes and told the TOTAL value of all of them (but not the prices of each individual one). You are then face with a pie prop. The outer "crust" would be a physical prop while the "filling" of the "pie" would be a circular screen. This pie would be split into 10 slices. Each slice has an outline to separate them.
You are then given a "slice" value. For example, if the total prize package was $12,000, each "slice" would be worth $1,200. Each prize is also assigned a pie flavor. These flavors may vary with each playing, but on holiday specials there would be at least one flavor that fits the theme (for example, pumpkin pie for Thanksgiving and Halloween and apple pie for 4th of July).
So here's the idea: "fill" each "slice" of the "pie" with a flavor corresponding to one of the prizes. The number of slices of a single flavor represents the price of the prize when multiplied by the slice value.
Also, to make it easier for the contestants, a display at the top would show the current bid for each prize and would update itself as slices are filled. I'm thinking about this for the method of filling the pie: contestant declares a flavor and how many slices (s)he would like to fill. The screen would fill the pie starting from the top and going clockwise. After making their decisions, they would be allowed to make any changes they wanted. For example, replace one of the blueberry slices with a strawberry slice. If any changes result in one or more "slices" of a single "flavor" being separated from the other slices of that same flavor (like this: A A A B B B B B B C A C), the screen would automatically adjust the pie so that all slices of matching flavors are next to each other). If the contestant is right about all three prizes, (s)he wins them. I'm also considering a prize of something like proportional amounts of the pies of the flavors for that playing for a year or something. (For example, blueberry, strawberry, and pumpkin are the flavors, and the solution is 2 blueberry, 5 strawberry, and 3 pumpkin; if the contestant wins, they also win a years' supply of pies of those flavors, with the actual number of pies they receive reducing down to 2 blueberry for every 5 strawberry for every 3 pumpkin). They win nothing if any of them are wrong.
This game could techincally also use a cash prize as one of the prizes, but it would probably have to be something like a fish bowl of $20 bills or something. The value of the cash would be narrowed down by determining the prices of the other two prizes and just setting the cash prize to the remainder.