The Japanese invented and perfected the original futon mattress for sleeping. ... And then Bedworks created the first layered foam-and-cotton futon mattresses for these new sofa beds. William Brouwer created the futon sofa bed in 1982. Bedworks first introduced Brouwer's invention to the world.
They help keep your Shiki futon from resting flat on the floor to provide additional cushioning as well as breathability. These also can be stored away to free up your floor space when not in use. In some Japanese homes, they are also used as whole coverage flooring or within pieces of furniture.
The biggest differentiator in the traditional way the Japanese sleep is that they sleep on the floor, on top of a precisely arranged combination of cushions and mats. At the bottom is a tatami mat, followed by a Shikifuton (or mattress) and a kakebuton (the duvet), and topped off with a buckwheat hull pillow.
A futon in Tokyo will be more expensive than one in Fukuyama due to the location and cost of living. A “good quality” futon can set you back anywhere from 10,000 to 100,000… depending on size and how LUXURIOUS you want it. A good median price is about 20,000–25,000 for a single with good cushioning for a foreigner.