Mike Leake's five-year, $80 million deal (plus an option year and a full no-trade clause) is about the going rate for a league-average starter right now, but Leake's history of putting up innings and getting ground balls made him the ideal fit for the St. Louis Cardinals, who also benefit by keeping their first-round draft pick on top of the two supplemental-round picks they'll get for losing Jason Heyward and John Lackey.
Leake has been extremely durable and consistent over his major league career, making over 30 starts in each of the last four seasons and throwing more than 1,000 innings for the Cincinnati Reds before the mid-2015 trade to San Francisco. He's never suffered an arm injury, even though he was worked fairly hard as a rookie by then-manager Dusty Baker, and his performance has gradually improved with experience; his three best seasons by ERA and FIP were his past three, 2013-15, and those would likely have been his top three seasons by Baseball-Reference's WAR had he not missed three starts with a hamstring injury after he was traded.
What Leake promises to provide the Cardinals is twofold: bulk innings and ground balls. The first is something the Cards need badly, the second is something they value highly.