From cars to clothes to household goods, products moved by shipping container got tied up at South Florida ports and could become more expensive after thousands of International Longshoremen’s Association members walked off their jobs along the East and Gulf Coasts on Tuesday in a contract dispute with shippers. A key question for consumers: How long will it be before prices start spiking as supplies shrink? “It’s probably not going to be too big a concern if it’s two or three days,” said Steven Carnovale, associate professor of supply chain management at Florida Atlantic University’s College of Business.