One of the most closely watched leading indicators of inflation on Wall Street has hit a record high, a sign that upward pressure on prices could last for months to come. The prices that dealers pay for used cars in the wholesale market jumped 5.3 percent from August to September, according to the Manheim Used Vehicle Value Index. It’s up 27.1 percent from last year. Used car prices have soared since the pandemic hit, when production snarls at automakers cut the supply of new vehicles as many Americans left urban centers for the suburbs, pushing up demand for personal vehicles.