Many price comparison websites make money off of commissions; when someone makes a purchase, they get a percentage of it. Others offer special placement for companies that pay. Many also use pay-per-click advertising.
Price comparison websites have become more popular over time, and their total revenue continues to grow. The more famous websites typically make most of their money by getting a percentage of deals they facilitate. If someone books a hotel room found on a price comparison website, for example, a portion of the amount paid goes to the website.
Many price comparison websites make money through paid placement. If a user looks at a list of possible choices, the sponsor will appear near the top. Most of these sponsored listings are marked as such, but this information does not have to be revealed in all locations, and some sponsored listings might look like regular listings.
Websites in general rely on pay-per-click and cost per mille (CPM) advertising campaigns, and price comparison websites are no exception. While many price comparison sites make most of their money through affiliate sales, they can also make a considerable amount through traditional online advertising. Travel-related ads tend to generate a significant amount per click, which is part of the reason why travel-related price comparison websites generate so much revenue.