The concept of exchange is, of course, vital in Social Anthropology. The Gift economy is rife in allotment society.
Here's one example from yesterday alone:
Joan told me that Big John (No. 79) had done some work on their front door for them - the paint had peeled off or something, and Big John had touched it up for them, but wouldn't even accept any payment for the paint he had bought and used. They had bought him a litre of whisky for doing it. But John had done a lot of digging on Big John's allotment while the latter was away (partly because he's done all his winter digging and was at a loose end), so it seemed a fair exchange to me. However, in the spirit of Mauss's The Gift, the bottle of whisky represents the bigger gift topping the last one, which leaves the recipient happily indebted to the giver, and thus perpetuates the cycle of gift-giving. That's in Social Anthropological terms - in human terms, all it means is that John and Joan were more than grateful to Big John for his generosity, and wanted to show him their appreciation.