They have a 400 foot version of this at Six Flags Over Texas they installed back in 2012- it's pretty tall.  And the scary part isn't the height as much as the wind at that level that moves you.
That said- first time I rode it with my oldest kid- I thought "this would be nice to take a selfie up here with her"- well, I got up there and thought "what if I drop my phone".  I mean, it could kill someone.
There isn't even a net at the bottom.  Needless to say, I'm shocked something hasn't happened at one of those before.