I'll still go with both the best and worst case example being Johann Santana with the Twins, They made the big trade with him coming off 2 Cy Youngs and a year of control. They got the much heralded return of 4 prospects. The prospects all crashed and burned, but MN was 2nd in the div that year and won it outright the two following years without him. If they had kept him they probably win all three years and would been no worse off. That's sort of the limits at both ends in one real case history.
Also notable that the Twins dodged a bullet in not giving him a crazy long term deal at 'only' 29, as he only had three more good years and was out of baseball after 4. The Mets ended up paying him for 6 - which actually wasn't terrible compared to terms people are predicting today.
Of course that's not the only possible future for Skubal, but it is among the real possibilities a FO has to consider.