Roaming has become cheaper and in some regions effectively free, yet a local plan is still the better option on many trips. The reason lies in how operators settle with each other.
Roaming is a commercial arrangement, not a technical one
When a phone connects abroad it is using another company's network. The home operator pays that company a wholesale rate under a bilateral agreement, then charges the customer whatever it chooses.
Those agreements vary enormously by country pair. A home operator with a strong partnership in one market and none in another passes that difference straight through as retail pricing.
Nothing about the underlying network makes one country expensive and another cheap. The cost is negotiated, and the traveller sees the result of a negotiation they were not part of.
Regional agreements create sharp cliffs
Some blocs have regulated roaming within their borders, so a phone works at home rates across many countries. Step outside the bloc and the rate reverts to an unregulated tariff.
Those boundaries are political rather than geographic. Neighbouring countries separated by a bloc border can differ by an order of magnitude in what the same data costs.
Fair use policies also cap the regulated benefit. Extended stays trigger surcharges because the rules were written for travel rather than for living abroad on a foreign plan.
Local plans are priced for local competition
A domestic prepaid plan is priced to win customers in a competitive home market. Data volumes that would be expensive as roaming are routine as a local package.
In markets where most people use prepaid mobile as their main connection, the packages are generous by design. Travellers benefit from pricing aimed at residents.
Registration requirements differ, and some countries require identity documents to activate a line. That step is the main friction rather than the cost.
eSIM changed the practical calculation
Devices supporting an embedded SIM can hold a second profile alongside the home line. The home number stays reachable for messages while data runs over the local plan.
Profiles can be bought and activated before departure, removing the airport hunt for a shop. The purchase is a data plan rather than a physical object.
Coverage still depends on which local network the profile uses. A cheap plan on a network with weak rural coverage performs badly outside cities.
Where roaming is the right answer
Short trips rarely justify the effort. A few days of moderate use on an inclusive roaming allowance costs less in time than sorting out a local line.
Multi-country trips with many short stops also favour roaming or a regional plan. Changing profiles at every border consumes the saving.
The deciding factors are duration, number of countries and how much data the trip actually needs. Beyond a week in one country, local capacity usually wins clearly.