(NYTIMES) - Imagine you are hunting online for a pair of square-toed slides from Bottega Veneta, one of the most-hyped luxury brands now. A new season pair can cost over US$550 (S$737) from the brand's website, an old-guard department store like Neiman Marcus or an e-commerce player like Net-a-Porter. But what if you chose to buy from Cettire, a website offering discounts of up to 30 per cent on the latest fashion styles? You would be a player in the multibillion-dollar luxury "grey" market, a fast-growing sales sector that has historically operated out of sight of most Western consumers. But with the arrival in recent years of firms like Baltini in Italy, Italist in the United States and Cettire, which listed on the Australian Stock Exchange at the end of last year, grey sales have been ending up in millions of digital shopping baskets. Unlike the illegal counterfeit goods found on the black market, the grey market sells authentic luxury products - but at a significant discount, usually between 15 per cent and 35 per cent, and with no contact with the brands. Through a practice sometimes known as parallel importing, grey market sellers take advantage of the varying pricing strateg...