I like your characterizations of where the ransom note - writer appeared to be coming from. Like he was some great big deal, and he was letting them know he was so great and so clever and powerful that he could pull off whatever, get away with it, and there was nothing even they...well-known and wealthy people...or anyone else for that matter, could do about it.
Not so much a ransom note, was it, really?
No, it was more of a self declaration that he wanted to communicate. Include in that the point that he even knew about the 118,000 dollar bonus. Oh, my, how very clever and "victorious" he is. See, everybody!!! See!!!
hmmmmm... You're right, maybe it was not truly set out to be a ransom note but more of a bragging and I am in control note. Maybe we need to stop looking at it as a ransom note.
The note also indicates that his obsession was not solely JonBenet, but carried over to her family. He was obsessed with JonBenet's world.