I'd guess that there's no extra cost for an operator like Vodafone if they have a roaming client using data. Mobile data will not go back to the home country an

I'd guess that there's no extra cost for an operator like Vodafone if they have a roaming client using data. Mobile data will not go back to the home country and peering costs are similar throughout Europe. Phone calls have to be routed to the home country but that's not a significant cost item.