If Buddy improves a grade on his defense and his court sense, then I could see him approach the $20 million/year mark. For me, Malcom Brogdan is a superior overall player. He just signed a four year contract that averages $21.250/year. In my view, that's the absolute ceiling for a Buddy contract.
If Buddy doesn't take that step up, then he's more like a very good 6th man, not a very good starter, which means considerably less. Take a look at the Lou Williams contract with the Clipps - 3 years for $25 million ($8 mill/yr), signed in 2018 when he was 31. JJ Redick, age 35, just signed a two year deal with the Pels for an average annual salary of $13.25 million. (I am making an assumption here that Redick is more of a 6th man type because of mediocre defense and ball handling skills). Dinwiddie, age 26, of the Nets, just signed a 3-year contract at an average of $11.5 per year. Terrance Ross, age 27 just signed a 4-year contract with Orlando for an average of $13.5 million per year. At the low end of the range is Lou Williams at $8 mill/year. At the high end of the range is Ross at $13.5 million per year. To really come up with his worth, the Kings would have to meticulously compare the above player's strengths, weaknesses, and respective ages with Buddy's, as well as look at additional contracts signed within the last couple of years. Just ballparking it, it looks like his range is between $13 - 20 million/year. And in my own opinion, much of where Buddy falls in that range will depend this coming season on the non-shooting elements of his game, as the shooting aspect of his game is pretty much nailed down at this point.