A Costco membership is often a good investment for families looking to save money on groceries, household goods, electronics and even furniture. If you purchase the Gold Star membership, you’re likely to save more than the $65 membership cost within a year. Meanwhile, the$130 Executive membership pays 2% rewards good toward future Costco purchases. But what if you literally invested those membership fees into Costco stock five years ago? How much extra cash would you have today? Check Out: Amazon, Costco ...