Vodafone has (for now) a data roaming rate of $2/MB when in Australia. On both of my recent trips to Aussie, I have kept my data on when roaming, as I decided a cost of $2/MB was affordable. So Vodafone got to make money from my roaming.
In Hong Kong and the UK, the roaming costs $10/MB. This is better than the old rates of $30/MB but still just too expensive. So what I have done is turned of data when roaming, and instead connect to wireless networks when I can find them.
This means that Vodafone makes no money at all from my roaming.
I’m overseas for a month. I could easily do 5 MB/day which at $2 would be $10 a day or $300 for the month. I wouldn’t be happy paying $300 for a month of overseas data roaming, but I would do so.
However no way would I pay $1,500 at $10/MB let alone $4,500 at the old $30/MB plan.
So if the telcos (Vodafone NZ can’t do it unilaterally) can get the price of data roaming down to semi-reasonable levels, I think they would be surprised by how much more people would use data overseas.