Most of the reason for the higher value on the cheaper fares is that they have a higher percentage of fixed taxes on them. In addition to the $5.60 TSA fee, there's the $4.30 per segment (up to 2) US excise tax + $4.50 (typical) passenger facility charge (up to 2). These last two fixed taxes are waived on awards. There's also the the 7.5% US excise tax on domestic fares which is proportional to base fare rather than fixed. It's pretty clear that WN is mostly using the base fare to calculate the points amounts (with some differences between markets). From the WN perspective using the base fare amount, the conversion rate looks to be pretty consistently in the 1.21 - 1.26 cents per point range (or 1.30 - 1.35 cents per point if you include 7.5% US domestic excise tax). This is why the conversion rate approaches 1.30 cents per point as you go higher up in fares in your table above. As a consumer, it's not really that relevant since it's not like you can avoid paying the taxes on the revenue fares.