RepairPal Certified shops can diagnose and repair your 2002 Chevrolet Cavalier. They provide transparent pricing with a minimum 12-month or 12,000-mile warranty on repairs and services.
You probably need to get a tech to check this out for you. The electric speedo can have a problem in the VSS (vehicle speed sensor), Powertrain Control Module or the instrument cluster or related wiring. Can't really price it until it's diagnosed.