If you require over 500K as a new grad you may need some luck actually.
A lot of places do not pay you median until you are BC and a few years out.
Also remember that "rural" has no real definition here. Many of these rural admins will just hire a locums instead, or some old guy/woman, or just anything not to pay a person with no experience national median salary.
If you put yourself in their shoes, its not that crazy. Remember, as an admin, your assessment of quality of a Rad Onc is fairly limited. You have references and board cert, prior credentialing.. really thats it. Its not like you can run cases with a new hire if you have no clinical knowledge.
A new grad might not show up, might take another job, might bounce, might not pass their boards. An 80 year old BC Rad Onc who has been credentialed at 25 hospitals in their career... theres very little risk of any of those things.
Its important to know your value but also understand that no one doctor is THAT special, especially outside academics. No one is going to stretch for a random out of town new grad.