This is because mail-processing costs are almost all variable while delivery costs have a very large fixed component.
Delivery costs have a very large fixed component whereas mail-processing costs are almost all variable.
Both mail-process and delivery costs are almost identical.
A child sits on the couch and plays a videogame
When the weather is  not good you really don't have any excuse.
three men are playing basketball
Lincoln glared and then spoke.
The dancers are under the lights.
The man is near the water.