But Paley was easy to underestimate, as he soon showed. In the late 1920s, the business worked this way: network shows were produced either by the networks themselves—so-called public interest, or “sustaining” shows—or by other businesses that “sponsored” a show, the way Pepsodent sponsored Amos ’n’ Andy. The broadcast schedule at most affiliated stations was therefore a combination of these sustaining programs, for which they paid the network a licensing fee, and the sponsored shows, plus whatever fare the local station itself might put on. NBC and CBS lost money producing the sustaining shows, but the idea was to make up the difference with the substantial advertising proceeds from the sponsored shows, of which a small portion went to the affiliates.

Tim Wu, The Attention Merchants, loc. 339