I can give you two more operators per diems.
Both are privately operated Gulfstreams for their owner. One based in ME & the other in Europe.
One is given US$100 a day per diem & the other Euro $100. This is basically for food & 'incidentals'.
Anything else, phones, transport, petrol, laundry, etc goes on the expense form.
I used this information before trying to get an increase. I was told to show receipts for breakfast, dinner & lunch. I did it honestly over a long period, most hotels we get complimentary breakfast either because of our FBO, loyalty, etc. Lunch costed $7 to $15 and dinner cost average $25.
I get paid a salary that I am happy with & I agreed before I joined, so I happily accepted the $70 per diem!
Admitedly, we don't spend much time in Europe, but we do get more when in Europe as needed!