Not necessary true! There is a huge disparity between the cost of these services to the companies and the price for the users. This means that there is still space for regulation.
Thats not true in many cases. The wholesale price cap is 7.70€ /GB. This is the price telcos have to pay other telcos for their users roaming. And this is more expensive than end-user price in the nordics/baltic region.
And now the providers have strong incentives to look for the cheapest roaming options, or if necessary band together to overcome predatory pricing. There is no reason for these wholesale prices to be that high and they will continue to be forced lower. The EU Parliament pushed for it to be 4 Euro, declining to 1 Euro over a few years, for example.
I would say there's space for competition, but the EU chose to not regulate to help competition, they chose to regulate to help incumbent South European operators, which are cash cows for well-connected partners.