Might be wrong but I always got the sense that even the most successful musicians throughout the vast majority of the last 2000 years lived in relative poverty, from minstrels to composers to virtuosos. Their art was used by people either with or seeking more money and more influence, the church, royalty, military, politicians and latterly the entertainment and recording industries, but that money and influence rarely dripped down to the musicians themselves, no matter how famous they were then or are today. The 1970's to 2000 era of musicians acquiring huge wealth was probably just a blip in historical terms.