Bob,
Not sure about the UPS pilots, but at FedEx their pilots, while earning a lower hourly wage, earn higher year on year salaries. The FedEx pilots get lots of credit time for their operation. If you think about how the night hub works, a pilot would come fly from MEM-EWR, depart at 2300 arrive EWR at 0300, leave EWR the following evening and be back in MEM at around 2200. This eats up alot of days of availability and has little flight time. The FedEx pilots get much more and they are paid time and 1/2 or double time on some occassions. If a pilot picks up a trip that is paid at time and 1/2. There is no limit on the amount of credit hours a pilot can be paid for in a month at FedEx. At UAL the most we can get paid for is 85 hours. These are just a few of the differences that allow the 727 captains at FedEx to earn over 250K a year.
The comparison of freight vs pax carriers is skewed by the schedule. They are not looking for frequencies (hourly service in business markets) they are looking for making sure the freight arrives on-time. A freight carrier may have thousands of customers (letters) on board a 727, when the best the airlines could do is about 145. (often the letters pay a higher fare than the pax!) There are enough dissimilarities to make the comparison apples-oranges.
In fact I bet the people that load the freight at the sort center in MEM probably earn more than the folks that load the bags at UAL or AMR for that matter. FedEx is committed to getting the product where it needs to be when it is supposed to be there. I am sure UPS operates in a similar manner.