Usually for an engineer or manufacturing professional, the cost of an item will depend to a large extent on the amount of material which will be used, if more material will be needed, the price will be more. However in the world of fashion the pricing rules of the manufacturing world are no longer valid.
The area of the cloth required for a popular model of nightgown or nighty (not the flimsy clothes worn by models and actresses) will be typically twice or thrice the area of cloth required for kurtis, and so the effort required to stitch the nighty will also be more compared to a typical kurti available in the market in 2015/2016.
However after comparing the prices of kurtis and nighties in the retail market, though the kurtis require half or a third of the fabric of nighties,most kurtis will cost twice or thrice the retail price of a decent quality nighty. Most retailers selling nighties will not charge more than Rs 300 per piece, usually price range is between Rs 200 – Rs 250 . On the other hand a kurti will typically cost Rs 500 – Rs 750 per piece, though the fabric, stitching required will be far less compared to a nighty.
The nighty sellers understand that their potential buyers do not have much money, staying at home, so they keep their margin low and aim for higher volumes. On the other hand women who prefer readymade kurtis will be working, and can afford to spend more, so these kurtis are priced higher though less material will be required. So for a person interested in reducing expenses, readymade nighties will be economical, while kurtis for daily use can be stitched at home.