That's true. Everytime when someone says "we're going to run out of oil" what they really mean is that "we're going to run out of cheap oil".
If you got the time, take a look at this page, watch the lecture from 8/29/2006, and in about the middle, the prof will show a chart and explains everything.
This is nothing new... I can' believe people actually paid money for this study. I could've done it for half the price!