關於worth,可見網友討論:https://ell.stackexchange.com/questions/181927/what-does-peeves-the-poltergeist-was-worth-two-locked-doors-and-a-staircase-me
I haven't read the book but I take worth there to mean "would cause a delay equal to that of two locked doors and a trick staircase". I base this on "when you were late for class", that is, in a hurry to get there.
I also feel it's an ironical/amused way to word it. Otherwise, it might write somthing like: "Peeves the Poltergeist cost two locked doors and a trick staircase"
另外,哈利與榮恩第一天早上使飛七不愉快,此處manage不知何意。(manage有「管理;經營;處理;控制;照管;駕馭」之意)