This is a fairly easy game to play that kids enjoy a lot. You can play it different ways but here is the main outline. Think of the game show "The Price Is Right".
First, get a list of things students want. It can be gifts for Christmas or birthday presents (about 10 will last you 30 minutes easily). Then, look up these on the internet. You can use Amazon to get the prices, or check specific sites for things like pets or cars. Save the pictures too, and show them on a computer screen if you can.
Since these are gifts, don't list cheap things like pencils, candy, or food (list things you would most likely unwrap). Instead, list school supplies so it is higher priced (higher that 20 dollars at least). Only 2 or 3 items under 100 dollars is good. The other stuff should be from 100-1,500 dollars. If they want a car, go ahead and get a really expensive one. The idea here is to practice reading and saying larger numbers.
After you get all the prices, divide the class up into at least 4 teams (4 or 5 students per team for more teams). Each team will guess the price of one of the items. The closest one to the actual price gets a point, and they are the last to guess the price of the next item. They also get to choose the next item to guess the price of. The second team closest to the actual price then guesses the price first, and then the third, fourth, and fifth team. Do the same thing for each round/item.
You can give them play money and have them count out the money to match the actual cost. This will help them understand the use of 20 dollar bills instead of 1, 5, or 10 dollar bills. Add coins to the higher level students and have them name how many of a specific coin or bill is needed (Ex. "$130.48", six 20 dollar bills, one 10 dollar bill, 1 quarter, 2 dimes, and 3 pennies).
With the last one, I often give each team a piece of small paper and instead of guessing the price in turns, they write it down. This can be for bonus points or just one point.