Although the amount of music available is unclear, he would be willing to pay "some" labels per stream, regardless of the number of ads running alongside those songs.
Amazon does not comment on the rumor. That said, it's easy to see that the company offers a free service. Although its existing pay-only services (Prime Music and Music Unlimited) have been relatively widely adopted with a total of 20 million subscribers in 2018, it is unclear how many of these people actually listen. Prime Music is more of a bonus than what listeners are looking for. Even if a free service did not have a larger catalog than Prime Music, it would have a much larger potential audience and make Amazon a more serious competitor in addition to selling more devices equipped with Alexa.