Hey, we're not all good with numbers so I don't blame you for this oversight.
Cespedes - 102 RBI
Goldschmidt - 99 RBI
Harper - 85 RBI
NL MVP? I count 41 RBI's in 39 games for Cespedes. Harper and Goldschmidt have played the entire season. Cespedes is already NL MVP in the universe in which Mike Vail is 1975 Rookie of the Year because he had a 25-game hitting streak after the Mets promoted him in late August. Over there, Vail went on to lead the NL in batting and RBI's four or five times, was NL All-Star six times, and held down RF for the Mets until 1985. MVP twice.
Cespedes hit .292 in 102 games with Detroit, posting .829 OPS. Maybe AL MVP, but not likely.
Over his career, YC is a .275 hitter, with an OPS of about .800. This is a hot-streak, not an MVP season.
Harper looks headed toward 40 home runs, about 95 RBI's, .330 - .335 average, and about 120 walks. That says Harper is having a typical Harmon Killebrew season for power, an Eddie Yost season in walks, a Sam Rice / Goose Goslin season for average, and slightly above a Goose Goslin season for OPS (typically .950 - 1.0).
Yes, Killebrew, Rice, and Goslin are in the Hall of Fame. Yost led the AL in walks a half-dozen times.
RBI's? Imagine this season with Rendon and Zimmerman hitting on either side of Harper, and Span leading off. More runners in scoring position and hitters after Harper making it risky to pitch around him.