For some brands (Volvo, Audi, GM) there are certain times of year Costco members get extra trunk money that stacks with everything. Right now the bonus money is with GM and Chevy, which is why people are getting free bolts in California and New Jersey (Chevy + Costco + state rebates).
Typically you have to be a Costco member the day before the program starts to be eligible, or sign up inside a new Costco location while the program is running.
