Let's say KC goes 20 this year. Over the next 3 years, he will make $7MM (2.2, 2.3, 2.5). If he goes back to school and gets drafted 10, he will make $7.5MM the next 3 years (0, 3.6M, 3.9M). He will be one year closer to his second contract. He will learn more about running a NBA offense being on a NBA team than being on a college team.
For him to get into the Top 10 as a sophmore, he would have to have usage that no Barnes player has had since Kevin Durant. He would absolutely have to ball out in Y2 to make up for the lost year of "potential" in the NBA's eyes. Considering the offensive issues, ZZ taking minutes away, and UT's offense not being run by most pro teams, it really makes no sense from a financial perspective to come back to school if you have a guarantee in the Top 20.