There are many answers to this question:

But the easiest way to explain why our rates are cheaper than our competitors is to refer to the business models of both Costco and Sams Club. All net travel rates for hotels, rental cars, cruises, condo weeks as well as all other aspects of travel get deposited into a national database that only travel agents can see. Typical travel agents like Priceline or Expedia then take these prices, add their markup and post those marked up rates on their websites for the general public to purchase. Similar to Sams Club, our members pay a low cost annual membership fee to access the same net travel rates we see as travel agents. We allow our members to utilize these rates for their personal travel needs for less than $1 a day!