Of two duvet covers in the same size, one sells for three times the price of the other. Where does the difference come from? Looked at through a manufacturer's eyes, the picture becomes clear.

The cost of a home textile product is roughly made up of yarn, weaving, dyeing and finishing, sewing, packaging and, finally, the brand's and the retailer's margin. In a cheap product, savings are usually made where you cannot see them. Shorter-staple yarn, a looser weave, less durable dyes, longer stitches. You will not notice at first. The difference shows up at the tenth wash.

There is also a technique known as filler finishing. Starch or resin-based chemicals are applied to a loosely woven fabric to make it look fuller and denser. It feels solid in your hands, but this finish goes in the first wash and the fabric's true state is revealed. Expensive does not always mean good, of course. Part of it is simply the brand margin. But it is inevitable that something very cheap has been cut back somewhere. The smart move is to judge a product not by its price but by criteria such as fibre, weave and the information on the label.