This is where I'm just letting my suspension of disbelief take over. The plot of the movie was that making an avatar body was ridiculously expensive, so the company recruited poor schlub Jake Sully to take his well-trained dead twin's place rather than let that avatar go to waste. 75 years or so later, they're just cranking these things out like hotcakes. It's not unheard of, but for a poor schlub like
me to afford to have my own personal avatar made, technology must have advanced pretty darn far.
Star Trek replicators and transporters.