Dylan isn’t in the same ballpark as the artists you are mentioning, I would have imagined his catalog to be an order of magnitude more valuable.
After 60 years Dylan has sold less than the Backstreet Boys. He produced relatively few hits compared to other renowned, popular artists. His style of music doesn't lend itself to vast commercial success. Someone will pay a premium to acquire his catalog because he's such a great artist and it's a large & influential catalog, however there is a practical limit to that.
I think you are mis-gauging what happens to music over the course of decades. Bubble gum pop and similarly positioned types of hip-hop etc do very well when they are in fashion, but don’t earn as much consistently over the long haul.
Dylan’s catalogue could plausibly still earn 50 years from now.