There's no difference. They are two names for the same thing. They tend to be used in different contexts, though. You talk about the expected value of a random variable and the mean of a sample, population or probability distribution.
Essentially, the EV is the long-term average value of the variable. Because of the law of large numbers, the average value of the variable converges to the EV as the number of repetitions approaches infinity. The EV is also known as expectation, the mean or the first moment.
The expectation is the average value or mean of a random variable not a probability distribution. As such it is for discrete random variables the weighted average of the values the random variable takes on where the weighting is according to the relative frequency of occurrence of those individual values.
Both warehouses have their own private labels, like Kirkland Signature at Costco and Member's Mark at Sam's Club. Those private labels are cheaper than name brands, and I've found Costco to have a much greater selection of those more affordable private label items.
Sam's Club accepts all major credit cards, including Visa, Mastercard, American Express, and Discover. Plus, customers can always pay with cash, debit cards, checks, SNAP and Sam's Club and Walmart gift cards.