[wolfbln]

Prepaid rates are not going down in most EU markets right now, on contracts it's another story.
Many countries have gone from 4 to 3 networks, what does not enforce competiton.
Given the fact that more and more data is needed, users are keep on paying more on prepaid.

EU roaming regulations from 2016/7 will have a Fair Use Policy in place severly restricting the "roaming-free" area in time or volume. The details are not set yet.
After all this was what the operators were lobbying for all the time. Their ultimate fear was that a user takes a cheap data SIM from north or east Europe and use it permanently on roaming.

To give you an example:
In Germany no provider sells you 1 GB below €10 on a monthly prepaid plan - that's an average price for Western Europe. In neigboring Poland you get 3 GB for PLN 3 (€0.70) from Orange right now. You see, that's the ultimate fear of the providers, that without roaming surcharges users take the Polish SIM on a permant basis. I think they have a reason, given the price difference. But this will be blocked by the EU which made clear "no permanent roaming" without surcharges.

Now, a player from outside of the EU (Ukraine) offers major EU markets on roaming with 1 GB for €6 or 5 GB for €11. The whole regulation becomes useless as the prices are being cut from outside.

To translate this for the US:
Let's say T-Mobile sells 5 GB on their $30 plan. That's one of the lowest prepaid plans in the US.
The new AT&T in Mexico can't cut this price very much lower, when they offer no roaming fees to Mexicans in the US. Right now, they charge MEX$ 200 (=$12) for 1 GB on their new plans valid all over North America. 1 GB for $12 is not a reason why people from the US would prefer a Mexican SIM card. It's more or less in line.
But the gap in Europe is 50 times as much. What do you do, when you are offered 1 GB for $1 roaming in the US by a company from outside? Would you still stick to T-Mobile US for data?
We can honestly expect that AT&T in Mexico is not so foolish to do this. But now an fictional operater from the Caribbean is just doing this....