*"Not really.  The extras are possibly still cheaper at around $50 a day or so, and easier than what a CG studio will charge". * Really? Where have you been making movies, China, or India?
I have been an extra in over thirty films, shot in Hollywood, Vancouver, Taipei, etc. and I have never had to work that cheaply! Maybe I should have specified that I'm not talking about replacing "principle" extras, ie, the background people who are right next to, or behind the actor in a scene. I'm talking about huge crowds, or armies, such as were created by WETA using their "Massive" plug-in for  Lord of the Rings. The technology is nearly there, and getting cheaper and more accessable all the time.