Ok, I was looking at things from a different point of view, but I get it now. A DNF prior to 2010 only cost 10 points, where as now a DNF costs 25 points.
DNF's must reward zero points. I think the reasons for this are obvious. One of the factors that lead me to suggest a system based on an exponential curve, was that under the current system, a driver that finishes the race in 11th place gets the same number of points as the driver that DNF. There is no incentive, aside from ego, to race for 11th place. Paying points for every finishing position creates incentive throughout the field.
If one makes an example of an individual driver competing for the WDC each race has a potential point pay out of x. With a season that consists of 20 races the season total,will be 20x. Therefore, any single DNF will cost 1/20x. It doesn't matter if x is 10 points, 25 points or as I suggest 200 pts.
Sorry for the double post, but rather than edit my earlier confused post, I figured I'd just recognize my confusion and move on.