How does radiology make as much as GI and cards when it seems all their starting salaries are so much lower?

Have talked to a bunch of fellows getting offers in each specialty. The GI offers are all routinely crazy (700-800k starting), cards very impressive (600k+), and rads almost always around 400k starting. These are averages I’ve heard, not all in the boonies or anything so sounds like fair comparisons. None of these are partner salaries obviously, they’re all starting.

Why is rads consistently so much lower when MGMA indicates radiologists make about the same as GI and cards?