The Hermes Birkin bag is losing some of its scarcity-driven appeal as second-hand supply grows and resale prices fall from pandemic-era highs. The shift is putting pressure on a luxury business model built around exclusivity, demand and high resale premiums. A Birkin bag bought at retail a decade ago is now worth, on average, 92 percent more than what its original owner paid for it, according to resale platform Rebag’s data cited.