From AppleInsider's "Eminem takes record label to court over iTunes royalties":

Busch then posed the question of whether service providers like Apple also pay the labels a fee for the digital files they eventually turn around and sell to consumers over services like iTunes, to which the Universal witness responded by saying, 'We asked them to pay a service charge for that, but we didnโ€™t always manage to collect itโ€ฆ'