From this message
(144856.13):
What do the draft balls translate into in terms of player salary and potential?
Salary
5 balls = $3,700 and higher
4 balls = $2,800 - $3,700
3 balls = $2,300 - $2,800
2 balls = $1,900 - $2,300
1 ball = $1,900 and lower
Potential
5 balls = 10 - 12 (MVP - All-time Great)
4 balls = 8 - 9 (Perennial Allstar - Superstar)
3 balls = 5 - 7 (Star - Allstar)
2 balls = 3 - 4 (6th Man - Starter)
1 ball = 1 - 2 (Announcer - Role Player).
So when you consider the +/- you can estimate where their salary (and skills) will likely fall.
For example, a 5 ball A- prospect could have a salary around $3,750, and a 4 ball B+ prospect could be right at $3,650. Really no difference there. At the same time a 5 ball A+ could be as high as $6,500 so understand the value of an A+.
Honestly, I would go more by the Grade rating than the star rating. Last year I went with a 4 ball B+, 3 potential, over a 5 ball A-, 2 potential because I knew the starting skills would be the same but the added potential was a benefit.