I've never understood why roaming charges are so scandalous. Surely the telecoms know if they dropped their prices they would make a lot more money?
Now add the enormous capital requirement of first building a countrywide network of GSM BTS, then upgrade these to UMTS, then to LTE (and, of course, always having to upgrade the backhaul links) and you see why mobile phone operators try to squeeze any penny out of the customer's pocket they can.
It's popular to blame governments for everything, but if market actors behave irrationally, there's nobody to blame but them.