Although dozens of travel-booking websites seem to fight one another for our travel dollars, what looks like healthy competition is actually an illusion. Agoda, Booking.com, Expedia, Hotels.com, Hotwire, Kayak, Momondo, Orbitz, Priceline, Travelocity, Trivago, and many others are owned by travel giants Expedia, Inc. or Booking Holdings, which together dominate the third-party online hotel-booking business.
Source: Hotel intel: How to find the best rates for rooms | KOMO
It’s a duopoly and the hotels voluntarily fix the prices such that they are generally the same price regardless of where you book the room. Second, many properties tack on “hidden fees” after you make your choices (watch out for Wi-Fi and “resort” fees).