As told by those who have worked with Werner Herzog and taken filmmaking workshops with him, the man is a beast when it comes to keeping a lid on his budgets. He's been rumored to put his own productions on hiatus for a day or two once he notices the cost of production creeping up, or foresees issues. He'll gather his team together and game out how to put the film back on track.
If his output of the last few years is an indication, his ability, and eagerness, to wear the hats of director and line producer is one of the keys to why he's continuing to make films. Financially successful ones at that.
The line producer is the day-to-day producer of the film and serves as the eyes and ears on the set conducting and coordinating the production's strategy and battling against disaster and setback along the way. They report directly to the producer and are given the role of "fixer" when major issues arise. They're also the "line" between the exec producer, director and principal cast and everyone else in the cast and crew.
...when the producer/director can't afford to hire a line producer then, for better or for worse, he needs to act like one on the set. Multitasking this way on the set means the director needs to be able to look at things from a line producer's perspective...
For low budget filmmakers who want to see their films through to the end and want to keep making movies, Film Strategy's PRODUCTION TIPS: 10 Ways Directors MUST Think like a Line Producer is a must read.