I think they are mainly charging for ad free playback. I've been putting up with the ads and they tend to be very annoying. There was one for a while where they

I think they are mainly charging for ad free playback. I've been putting up with the ads and they tend to be very annoying. There was one for a while where they would outright yell "Trojan Man" and talk about how thin and pleasureable it was while making gasping noises. Another would yell "Ad-vanced Auto Parts" at you. They are also smart enough that they pause when you mute the volume in an attempt to force you to listen to them (I have headphones so I just put the headphones down).