Ive seen plenty of airports charge for a trolley, including LAX, so MAN is not alone.
More to the point, when people are willing to pay less and less for flights, and airlines such as Ryanair willing to pay less to use the airport too, I wonder how people expect a business, to which MAN is, to make money (or in the philosophy of wanting to pay less do people expect an airport is purely a service to cater to their every whim, and not in fact there to make money for future regeneration, to which MAN is planning at this moment in time?)