Not really apples-to-apples considering how much of the finished car Tesla manufacturers. Other car companies make very few of their parts. Tesla makes almost every part.
Tesla does not make almost every part. I have talked to multiple Tesla part suppliers and can assure you that Tesla purchases both individual parts and entire subsystems the same way every other automaker does. Tesla has inhoused a couple of components that are typically done by specialized companies, such as their seats.
Tesla is defiantly the most vertically integrated car companies. But that different then saying they don't have lots of suppliers.