Yes, Geico really is the cheapest car insurance company for most drivers in the United States. Geico is very cheap because it sells insurance directly to consumers and offers a lot of discounts. Direct sales of insurance to the consumer eliminate the cost of middlemen and allow Geico to have far fewer local offices and agents than companies like State Farm and Allstate. Having a smaller agent network reduces Geico's overall costs, so they can transfer those savings to consumers.
Every insurance company determines its rates differently, so even though Geico is among the cheapest car insurance companies, the best way to ensure you're getting the cheapest rate is to compare quotes from several insurers.