Ghost signed a 6 year deal that covered his RFA years coming off a bad season, after an ACL tear and a bad groin injury, security mattered to him b/c he could blossom or get injured once again. Big underpay off 2017-18, but not off 2018-19.
Couts signed his deal after the 2015-16 season after seasons of 39, 37, 39 points. He had 34 points the next year, was injured again, and probably was happy that he signed that deal that took him through his RFA years - I doubt he envisioned he'd go from a solid defensive 2C/3C to one of the top centers in the league in 2017-18.
Hindsight is always 20/20.