Apple and Google may mark their apps up less than the average department store or grocery store, but it marks them up a hell of a lot more than most highly-efficient retail operations. Walmart marks up around 20%, and Costco never marks its products up more than 14%. And actual retail stores need to pay for their property, their employees, transportation, and utilities to keep their stores running. Apple and Google have none of these expenses. Additionally, both Apple and Google only operate app stores as side businesses to help sell their high margin hardware or get people to look at ads.