FOR A MEAGER $34.99, any vaper over 18 can purchase one of Juul Labs’s metallic e-cigarette devices. For a not-so-meager $5,000, that vaper, should he be so inclined, could slot his nicotine conveyor into a glittering 18-karat gold case from Florida jeweler Miansai. With sharp lines reminiscent of a vintage Cartier lighter, the gold shell is certainly elegant, but even Miansai owner Michael Saiger finds it’s curious that someone (it has sold 15 of these cases) would slip a four-figure case over an inexpensive Juul. “I do think that it is kinda funny,” said Mr. Saiger.

Yet...