$79M is governmental chickenfeed, given how much this service improves the quality of life of its citizens. For perspective, it's moderately less than the cost of one (1) F35.
The government has already been trying to do everything they can to run the USPS into the ground, something needs to be done about these treaty deliveries or a continual increase in volume is going to harm the postal service (I don't know what that something looks like, maybe make the federal government pay the cost difference for these treaty deliveries since the postal service is required to deliver them).
That said - again, you're quite right that we're getting a lot more for our money spent with USPS. Surely there have to be less expensive and more worthwhile ways, than the F-35 project, to run a jobs program!