Mattresses are manufactured in four basic sizes: single, twin, queen and king. Most mattresses today are made with inner coil springs to provide comfort and support at the same time. Most mattresses are sold with matching box springs that go underneath the mattress to provide added cushioning.
Over time, mattresses tend to become compressed in the parts where they are slept on the most, and to lose their shape. This happens more quickly in less expensive mattresses. One way to extend the life of a mattress significantly is to flip it every month or so. The mattress should be flipped vertically as well as turned around from head to foot to spread the wear equally. This will prevent any one spot from becoming excessively worn.
Water beds incorporate mattresses that are basically giant bags with water in them. Most of these types of mattresses have baffles in them to prevent excessive wave action. Some people find water beds very comfortable, but they are not recommended for anyone who has had back problems, as they do not provide the support of a conventional mattress, particularly in the lower back area.
Cheap mattresses can be purchased for $200 or $300, but these tend to be relatively low end and will not provide the comfort or the durability of a more expensive mattress. You can probably expect to pay upward of $1,000 for a quality queen-sized mattress and boxspring. The extra expense probably means less expense in the long run, however, because a high quality mattress will outlast a cheap one by a number of years.
There are various alternatives to mattresses. Futons can be used to sleep on, and are more adaptable than mattresses for other uses such as couches. Futons are also substantially less expensive. In tropical climates, people sleep in hammocks, although people who have grown up sleeping on mattresses often find this difficult and uncomfortable. When traveling, a small foam or inflatable pad can be used for sleeping, although it is generally agreed that these are nowhere near as comfortable as a mattress.