Ijewelry.com? Dead. Firstjewelry.com? Dead as well. Miadora, Adornis—so many online jewelry retailers are but a memory. And for a moment, it seemed that Blue Nile was destined for the same dot-com dustbin. But today, the Seattle-based e-tailer hasn't merely survived, it's thrived. In 2006 it racked up $250 million in sales and could hit between $290 and $300 million in 2007. Those are striking numbers for a company that's been around for only eight years. Unlike past mass market competitors, Blue Nile scares independent jewelers because it sells high-end items. Its $5,600 average price for an engagement ring far exceeds the national average of $3,200. In an interview with National Public Radio last year, chief executive officer Mark Vadon identified the company's competitors as Tiffany and independent jewelers. (Blue Nile turned down JCK's request for an interview.) “Our biggest c