His 3.32 ERA is largely carried by what he did in Tampa and Detroit. His 3.84 ERA in Boston was respectable. But at age 31, it was the a wrong time to give him the largest and longest contract in team history. Especially with all the young talent the Six had that could have been extended (assuming they were amenable). And Price was great his first year, but his last 3 were mediocre at best. In 4 full seasons in Boston, Price was only worth 10.3 fWAR, 4.4 of which came in his first year. Over that stretch, he was outperformed by Rick Porcello, who signed a shorter, cheaper deal at a younger age.
In the end, the Price contract was part of the huge salary mess that lead to dismantling the 2018 team in favor of the cheaper, less effective team you see today…