Each play in Pandora is only listened by one and only one person. Each play in terrestrial broadcasts is listened by potentially thousands of people, depending on the demographics of the covering areas. So it is uni-cast vs broadcast.

If the OP understands the difference, has a reasonable estimate on the number of listeners for broadcasts, and is reasonably good at calculation, he would find out that Pandora actually pays more.

Plus, Pandora provides more and better services to the listeners for the artists than terrestrial broadcasts. A simpel example. I am working and listening to Pandora. A nice song catches my ears. I could immediately look at the song, its album, the artists, and all other related information. Terrestrial broadcasts don't provide such a service. So Pandora is providing a deeper and more comprehensive marketing for the artists than terrestrial broadcasts, and it reaches more diverse population. That is a big benefit that the OP does not consider.

<edit> grammer