When Ashlee Laird, 32, a high school adviser in Houston, was planning her honeymoon to Italy in 2015, a friend suggested she look at Costco Travel, the travel division of Costco Wholesale’s retail membership club that operates warehouse-scale stores. Through Costco, she booked an eight-day trip to Rome and Florence for two for $3,800, including round-trip flights, hotels, daily breakfast, private cars to and from the Italian airports, first-class train tickets between the cities and $400 to spend on tours, which they used to see the Vatican and the Colosseum and take a pizza-making class.

In comparison, their flight alone is running $2,600 for two this spring.

“There was no downside,” Ms. Laird said of her Costco package, noting that the travel agent assigned to the couple kept in touch before, during and after the trip.

In addition to bulk supplies of toilet paper, KitchenAid refrigerators and giant packs of canned salmon, Costco sells trips to Europe, as well as Riviera Maya resort stays, Alaska cruises, safaris in East Africa and Disney theme park trips.

Wholesalers like Costco are among a number of membership clubs and associations that, in addition to other benefits, offer discounts on travel, including rental cars, cruises and tours.