Depends on the school. Some of the NPC’s we ran for D17 were off by several thousands of dollars, some were spot on. (And Colgate, for whatever reason, was more than ten thousand off, but the difference in the actual offer was in our favor.) There’s wide variation in reliability.
And we’re never-divorced parents with no weird business ownership or investment real estate situations. Once you get any degree of complexity, NPCs can go very badly.