These are factors that go well beyond simply how much the machine costs. You also need to consider the size of the area to be cleaned and the manpower available to do the work, along with the weight and ergonomics of the unit, its manoeuvrability as well as its durability and “repair-ability”.
Keep in mind that vacuum cleaners are not just for cleaning carpets. They also offer excellent results on hard floor surfaces while improving indoor air quality to boot. A recent study shows that using a vacuum cleaner rather than dust mopping reduces the need for burnishing by 60%.