Norman Greenbaum of Spirit in The Sky fame apparently made at least $2M from the royalties to that song as he was the sole writer and kept all rights. He is still coining it in all these years later.
Opposite to that are a number of groups/singers that got next to nothing from massive hits.....mainly because of bad advice/management eg The Verve that wrote and recorded Bitter Sweet Symphony. They used some rifts from a Rolling Stones record, we're sued and had to forego 100% of the royalties to Jagger and Richards (J and R did give them a pittance as a gesture many years later).
Opposite to that are a number of groups/singers that got next to nothing from massive hits.....mainly because of bad advice/management eg The Verve that wrote and recorded Bitter Sweet Symphony. They used some rifts from a Rolling Stones record, we're sued and had to forego 100% of the royalties to Jagger and Richards (J and R did give them a pittance as a gesture many years later).