The Big Plot Hole - Spoiler

Rating: Null/10 (29 March 2008)

As stated in The Terminator, "Only living things can travel through the time displacement field. Nothing dead will go."
That is the whole point of the first film.
The T-101 (or T-800 or Arnie) looks human.
So how do the T-1000 (in T-2) and the T-X get through?
If metal can get through then why not bring future weapons?
In the TV Series, we are back to T-800s (large sub Arnie types) but they are supposed to be from even further in the future.
Are we to believe that the future machines are subject to the "market economy" as we are. So they can no longer afford to send expensive liquid metal machines -("Sorry lads but it is no longer cost effective to try and rule the world this way. This liquid metal stuff has to stay here in the future where we can keep it safe."), and they are just sending any old thing they can find?