My company publishes a list of per diems by country. The most common is $45, although they changed that to 45 euros for the EU after the dollar tanked. One notable exception was in Russia, where the rate was $100 for a long period of time. This was reduced to $50 after it was noticed how many people insisted how important it was for them to be in-country. Lots of profit for some people.

We also have the benefit of a sedan service to take us to the airports. The fee paid by the company to the limo company is pre-defined per route and includes a fair gratuity for the driver. The trouble is, I always feel obligated to tip $10 or so upon arrival, since I'm not sure how long their owner takes to pass on the previous payment. I cannot get reimbursed for this so I generally eat it.