Prince plays on a high school team with 4-6 other D1 players. That means he doesn't have to go out and score 30 point, get 10 assists and 10 rebounds per game. If scouts were seeing those number constantly I'm sure he wouldn't have dropped as much. Players that are top 10-20 can stay there while playing on teams like those because they are clearly the elite of the elite. For others it hurts them some.
Also, like david said he didn't play in the EYBL. No matter what people say I do believe that players get docked some if they don't play in the EYBL. However, Prince is most likely playing with the Southern Stampede this upcoming summer so that shouldn't be a problem.
At the end of the day I think this is how it plays out. There are the elite of the elites, top 10-20, the real good elites, 20-40, and the regular elite, 40-100. Not much separates 50 from 80 sometimes. It's about your personal preference.