Holy God, there is literally almost nothing similar about Rusney Castillo and Jason Heyward. Rusney isn't considered an overpay either, except to people that unrealistic expectations about how quickly he would transition to MLB and people that completely discount injuries. As Hillbilly noted, if you use about $7M per win (which as he notes is probably low at this point), Castillo can easily meet his contract just basically by staying on the field. Even his weak half season put up .8 bWAR last year.And you think that Jason Heyward belongs in that company? On current level of performance? On projected future? You (or any GM) willing to give him a contract in excess of 200 million better be pretty confident in their evaluation of the defensive component of his skill set because the offense sure as hell ain't worth 200m.
As a point of reference I would bring up the name Rusney Castillo - they are actually rather similar players - excellent defensive OFs with limited batting skills. Heyward's offense is better but not at elite levels. Now Rusney's considered an overpay at his current 10.3m a year. Is the difference between Castillo and Heyward worth 20 million dollars a year?
Heyward's offense is certainly better and though it's not elite, there's plenty of room to grow and a lot of scouts cited the Braves for screwing him up (as they did the Upton brothers and some other guys that saw their swings deteriorate while playing in ATL). He was noted for making much better contact after some changes in STL and after a slow start, his splits took off after the All Star break, to the tune of .317/.397/.469. And at 26 years old (two years older than Rusney, with already 31+ WAR under his belt), he's coming into his prime. A premiere RF defender, who can put up a .850 OPS in today's environment with room to grow into even a better hitter is easily the most valuable position player on the market.