If the seller of a large collection of music that was ripped from CDs also delivered the CDs to the buyer of the collection that would be fine. But, if the seller makes multiple copies of what was ripped, that is a copyright violation. It is "fair use" to take your personal collection and convert it to another medium for your own use, but, you cannot sell or even give away that converted collection. If I made copies by ripping and I gave away the CDs that were copied, that would be a violation too.
If I did not did not give away or sell that collection and the recipient wants that music, that person would have to buy that music and that is fair for the artist or the owner of the copyright.