Costco is becoming a huge threat to car dealerships by offering one huge perk

Costco is becoming a huge force in the auto world. The warehouse retailer sold 400,000 vehicles in 2014, twice as many as in 2008, Bloomberg Business reports. "Without fanfare, the membership-only merchant better known for selling flatscreen TVs and jumbo-size boxes of cereal has pulled within spitting distance of No. 1. car retailer AutoNation, which sold 533,000 vehicles last year," according to Bloomberg.  Customers prefer Costco over traditional car dealerships for one reason: prices are ...