where is the cheapest place to buy cake boards and boxes from?
This info is available here on CC and on google by using these keywords in your search"drum", "cake circles", "boxes".
Cheapest isn't always best. If you aren't purchasing locally, you should also take into consideration what companies offer free shipping.
Walmart has plain corrugated boxes in their office supply section that work. $1 - $2 each
I use wwwbrpboxshop.com
love them! free shipping, great prices, etc.