In my point of view and from my experience "per diem" should not be accounted for as real wage money. I believe that the decrease on the pilots salaries over the past 10 years is also connected to the point of view that "Per diem" is part of the package. It should not be. It is a money calculated for you have your meals when out on the job.
The major airlines paid that in envelopes. Once you arrive at the hotel of your night stop you will have an envelope with your "per diem" in.
Don't count on hat money. There are some cities where you will need more than those 70 Euro if you want to have 2 nice meals. Not luxurious, only nice.
Let us all not make our profession even less respected. Managements already don't think much of us...
Cheers.