Here's an article from Forbes looking at last years draft and the projected salaries.
https://www.forbes.com/sites/jasonb...round-rookie-salary-projections/#700da3d0642d
Going top 5 versus something like 20th makes a significant difference, though even the last guy in the first round will sign a guaranteed contract worth a few million bucks, so hard to pass that up I would think. Only chance as I see it is that he gets NBA feedback and they tell him a proven jumper could vault him from mid-first this year to high lottery next year. More likely though the scouts figure he can develop the shot (his form looks pure to my untrained eye) and it doesn't make a huge difference.
I'd guess then the question would be the strength of this year's class versus next. I have heard next year projected to be weaker, but those things change.