China’s secondary semiconductor market is seeing a sharp run-up in memory chip prices as global supplies tighten, though vendors say the rally faces an awkward conundrum: the price tags might be higher, but the buyers are disappearing. “We’re looking at high asking prices, but no buyers,” said Cai Zhaojie, a merchant who sells electronic components at Huaqiangbei, the vast Shenzhen wholesale hub often described as the world’s biggest electronics market. The mark-ups on memory products had become...