And the French are subsidising Latvian agriculture, universities, roads, and infrastructure. I don't think it's fair to evaluate this policy isolated from the rest of EU policies.
It's possible that visitors to Lithuania were paying high termination fees to the local telco and subsidizing the native subscribers.
Assuming the telco profits remained static (which may or may not be true) presumably someone was paying these costs before and if it wasn't Lithuanians then who was it?
But the grandparent post was someone from Latvia saying 'this is terrible our prices have gone up' which was followed by someone from France saying 'no this is great our prices have gone down'.
Someone's paying for it, and I doubt it's the Telcos who are losing out.
Oh, telcos absolutely lose, because there were a few companies present in most EU countries and somehow most of them charged for roaming anyway only because they could - it cost them nothing extra.