I call this activity the "bidding game" and I've used it on numerous occasions with Year 4.
The class is divided into groups of six. I give each group a variety of coins amounting to pound;6. On a piece of A4 paper, they copy from the board drawings of six items on a common theme, for example Tsunami relief: bedding, toothpaste and brush, towels, blankets, disinfectant, soap.
Each group has to place a "bid" on all six items. When this is complete I ask them to tell me their bids. The highest bid secures the item and the winning group ticks it off.
The groups then have to repeat the bidding process on all six items, with me accepting the highest bid until one group has successfully ticked off all the items.
This activity promotes much discussion and decision-making as children need to realise that a minimal bid on items already ticked off by their group allows more capital for unsecured items.
The activity works well with mixed-ability groups and the children enjoy it immensely, while increasing their understanding of the value of money.
SMT and Year 4 teacher, Wilberfoss Primary School, East Yorkshire