A mixed bag of Halloween sweets is a small economy waiting to happen. Someone loves the chewy ones, someone wants the little chocolate bars, and someone is prepared to accept almost anything if it comes in the right colour wrapper. Put the bag in the middle and give negotiations a chance.
The exchange rates will be deeply personal. Two things you are only mildly interested in might become one thing you actually wanted, which is an excellent piece of business. Add one particularly desirable sweet and suddenly there is a valuable commodity on the table. A biscuit tin lid can serve as the trading desk if the occasion calls for infrastructure.
I like the idea of everyone getting a slightly more ridiculous title as proceedings develop. Head of Marshmallows. Director of Small Chocolate. The person who has quietly cornered the market in something nobody else noticed. Any attempt to produce a sensible price list should immediately be undermined by someone announcing that the orange ones are their favourite.
Keep the trades cheerful, let people keep what they want, and remember that eating the assets is a perfectly acceptable exit strategy. Halloween already provides the costumes and the tiny packets. Giving the sweets a short career in international commerce seems like a reasonable extra.
