Saks Fifth Avenue is purchasing Neiman Marcus in a mega luxury fashion merger.John Greim/Getty ImagesSaks Fifth Avenue is purchasing Neiman Marcus for $2.65 billion amid luxury retail challenges.Amazon and Salesforce are taking minority stakes in Saks Global, the new company.The news shows how hard it is for department stores today — particularly compared to luxury giants.In a deal that shows just how hard things are getting in the luxury retail space, Saks Fifth Avenue's parent is purchasing rival department store company Neiman Marcus for $2.65 billion, The Wall Street Journal reported.Amazon — which has long tried to boost its luxury offerings as part of its "everything store" concept — and Salesforce are getting in on it, too, with both taking minority stakes in the new company, Saks Global.