Not that I think that CGI is cheap, but spending millions in computer graphics with today's powerful hardware sounds absurd. So, something else must be it.
Edit: Oh, please. CGI is cheaper than actual props. ET the movie would be way cheaper to remake today than 40 years ago.
I'm sure even with the advances we have seen that the costs have not dropped even slightly for a per hour like break down for rendering anything.
In fact this space is such a hot bed for rampent price gouging, hedgeing against the movies production, shell companys as standard opperation procedure to absorb and off set potential losses, the fine fucking print is almost illegible... Its surprising any money is "made" anywhere.