The 5 dollar challenge would be really fun. My wheels are already turning just in case.
The idea of multiple receipts is genius. You can find the best bargains at many different stores.
It's like many of those cooking shows where they go to a store with a budget...you'll just have to make a special trip for this throwdown with $5 in hand. Easy to do.
Also think of the dollar menu at fast food places...good source of proteins/lettuce/mayo, etc...(HEAVY TOMATOES, ONIONS, and PICKLES!!!!)
The seafood guy at the store can sell 5 shrimp...that would cost a buck or so.
Spaghetti sauce can cost around a dollar (for the shitty stuff)
Oh, and Paul can list in the rules a "Pantry" that we can all use free of charge.
For example, the Pantry has:
Salt,
Pepper,
Italian Herbs,
Eggs,
Flour,
Sugar,
Hot Peppers (dried and fresh...cooks choice)