That’s how many turns the subway system’s most high-traffic turnstile — No. 602 in Fare Control Area R238, located in Grand Central-42nd Street station — is estimated to do in a year. That’s more throughput than some whole transit systems combined. These durable three-armed machines called tripods are designed by a company called Cubic, which also oversees the MTA’s fare collection system. And boy are they built to last.