The question "Are memberships to warehouse stores like Costco worth it?" The answer to that is tricky depending on how large your family is, how well of a couponer you are and what you buy. With Costco now taking food stamps it maybe worth it to some people but personally I don't believe it can be for the average family.
The memberships start at $50 a year and go up to $100 for an Executive membership. With the Executive membership you get 2% at the end of the year in the form of a rebate check but unless you spend over $5,000 a year it won't pay for itself.
So you want to shop at Costco without a membership? Did you know you CAN do that? How? Have a family member or friend buy you a $20 cash card - Costco's version of a gift card - and you can enter the store with that and buy stuff. Even if you go over the amount on the card you can still pay the rest with cash or a debit card (non-members can't write a check)! So skip the membership fee and get someone to get you a cash card instead. You'll need to have the friend/family member to refill it for you since non-members can't refill the cards either.
As for prescriptions... under FEDERAL law you don't have to be a member to use the Costco Pharmacy! Members and non-members can use the pharmacy and get the same great prices!