Why pure Silk fabric is so expensive:

Silk has a long history in world. Silk is a natural protein fiber, some forms of which can be woven into textiles. Silk is produced by several insects; but, generally, only the silk of moth caterpillars has been used for textile manufacturing. Silk is one of the strongest natural fibers, but it loses up to 20% of its strength when wet. It has a smooth, soft texture that is not slippery, unlike many synthetic fibers. Sericulture, or silk farming, is the cultivation of silkworms to produce silk. 

          

The entire production process of silk can be divided into several steps which are typically handled by different entities. Extracting raw silk starts by cultivating the silkworms on mulberry leaves. Once the worms start pupating in their cocoons, these are dissolved in boiling water in order for individual long fibres to be extracted and fed into the spinning reel. Silk has a high emissivity for infrared light, making it feel cool to the touch.  Silk is used for clothing such as shirts, ties, blouses, formal dresses, high fashion clothes, lining, lingerie, pajamas, robes, dress suits, sun dresses and Eastern folk costumes.

To produce 1 kg of silk, 104 kg of mulberry leaves must be eaten by 3000 silkworms. The major silk producers are China (54%) and India (14%). Silk's attractive lustre and drape makes it suitable for many furnishing applications.  It is used for curtains, upholstery, bedding & interior home decor.