Points are not exactly tied directly to the cash price.

The points multiplier (number of points needed per dollar of base fare) varies.

Currently, it's anywhere from 72 to 80 points/$1, with the occasional 70/$1 redemption rate, and very rare 60/1$ rate some people have reported finding.

Basic strategy: Never redeem points for AT or BS fares. On WGA, you'll get a better effective redemption rate on lower price fares due to the relationship of fare vs taxes & fees as mentioned earlier. Check each base fare and redeem at as low a conversion as possible (72, 74 is better than 78, 80). On higher fares, factor in the points earned on a cash fare when comparing.