Costco offers savings in areas many members don't think about. Image source: Costco.Most people think of Costco (NASDAQ: COST) as a place to save money by shopping in bulk. That's certainly one way to keep more cash in your pocket when visiting the warehouse club, but it's not the only one.There are many things you should always buy at a warehouse club, but Costco's shelves, website, and store-within-a-store areas also offer some not-so-obvious ways to save money.