Hi Grambo,
To be a bit more specific:
As someone just mentioned, you have freighters that give you more (sometimes much more) money than the industry average, pax airlines included (UPS, not too sure about Fed ex, and some companies in Asia...). Then you have some very bad ones too ( too many of them).
What cc the majors, pilots may fly both pax and freighter fleet, no difference ( Air France, Korean, Japan Air Lines B744 pilots,..)
Then, you have f%++kg managers in a few companies who like to start different salary scales, with the freighter pilots on a lower scale..(Cathay,..)
'hope it answers yor question