Basically, the students use vocabulary items, or standard sentences, as money. The teacher is a shopkeeper, the students are the customers. The students buy objects that they need to complete a drawing or plan. In order to buy the object they need, they have to produce the words which are the price of the item. For example, to buy a chair for a house, the student must answer correctly the question 'What time is it?', or, 'Can you count to ten?', or, 'Name three things you can find in a classroom.'
We often play it with my 10-12-year-old pupils. It takes a lot of time to prepare for it, but it works very well. My first lesson dealt with animals. Each student had a picture of the main body, without the limbs and other body parts. I had drawings of paws, paws with claws, hooves, ears of different sizes and shapes, tails of different size, length and colour. All these items were cut out. I was the shop-assistant, the children were customers. The prices of the items varied - a long tail cost two words from their active vocabulary, an elephant's ear, let's say, cost a standard sentence, e.g. 'I'm sorry, I don't understand you. Can you repeat it, please?'
When attending to a customer I asked a lot of questions: 'Would you like to buy this tail?' (showing on purpose the one the pupil didn't need), 'What colour?', 'Do you want a tail bigger than this one?' So the number of questions that you can ask is just infinite. After buying an item the pupil had to glue it to the body on his card. Then coming back, he bought another item until the picture was complete.
So, you can sell the items necessary to build a house, to lay the table, clothes, vegetables to cook dinner, etc. If you don't want to waste your time on drawing, you just cut out pictures from anywhere. If a pupil does not know the necessary words - the cost of an item - he has to go find them and then come back.
In my groups (elementary) this activity works very well. They like it very much, even the queuing!