I think it is bigger than you think.
Really, star or not, if you get the minimum wage starter, then it becomes easier to retain your stars. Fr example, if the Sox still had Margot and Allen, sure neither are stars, but also maybe they do not extend Eovaldi and repeated extend Bradley. Now while Allen is hardly stellar, we would say the same thing about any prospect who gave us what we have gotten from Eovaldi, who has given us 105 IP of 5.57 ERA (86 ERA+) since signing that deal after 2018.
That representant close to $85mill i right there. Certainly not enough to retain Betts on it's own, but a big chunk of it.
And the decisions can be piled on to it. Was the Sale extension done (which it clearly appears to have been) because he was injured and unable to pitch? Should that have been done? That's another $145 mill and we still have to replace him anyway. And how many of those 5 years will he be effective?