don't know about the Highlander but will try to find my invoice for that and see what is included. I note for the Tacoma the only "safety" addition was the sway control (which some folks pan and others like) and the rest was longevity related issues.
the receiver can be purchased much cheaper than the Toyota version, so that can be left out of the equation, comparing to the factory package. I really thought that some things would be added like extra leaf in the springs, larger brake drums, etc.????
bumpy