The median monthly paid search spend is highest for consumer brand manufacturers and lowest for web-only retailers, according to a Digital Commerce 360 analysis of data from Semrush, a provider of search marketing technology.

But big retailers often spend a lot more than their smaller rivals. Amazon.com Inc. (No. 1), for example, averages more than $36 million a month on paid search spending. Other big spenders in this marketing arena are such big companies as Apple Inc. (No. 3), Dell Technologies Inc. (No. 17) and Microsoft Corp. (No. 89).

But by far the biggest paid search spender, according to Semrush, is Alphabet Inc., the parent company of Google. Alphabet sells a wide variety of products, from smartphones to home-automation systems, and when it spends on paid search, it effectively is paying itself. That no doubt makes it easier to justify its massive budget for paid search.