Courtesy of Brian Sommer, I saw this study by Harris Interactive that the average US employee spends $ 693 in international roaming calls on an overseas trip. Initially I was cynical because it is sponsored by Brightroam which sells an alternate SIM card. But the more I looked at the sample size and composition the more believable the number looks.
Adjusted for taxes that only buys 100 to 400 minutes depending on what part of the world the trip is - not unreasonable usage for say a week's trip with an employee checking voice mail, taking an occasional call from the home office, calling families etc. And frankly, data roaming is also expensive so number of minutes used for calling may be even less.
Before you choke on your sake and scream at your employees, blame yourself. For allowing providers like AT&T to charge prices of up to $ 4.99 a minute from some countries. You should scream at the EU for capping their own telco roaming costs but letting US providers get away with no caps. You should scream at device manufacturers like Apple for not allowing for unlocked SIM on the iPhone.
And only then should you should scream at your employees for not using Skype, for not renting a local mobile when they are overseas, for not using a local SIM card etc.
So scream a lot. Just not while you are mobile roaming overseas:)