Currently these charge points cost more than at home, and i believe it will stay this way. There is more overhead and more companies connected to the highway chargers so more people looking to make a profit. There is also the fact that currently ( and thats what these laws want to change ), you need some kind of subscription to use these public chargers, so even more costs :)

Dont get me wrong though, its not like public charging is like 2€/kW vs 0.35kW at home, but there is like a 10c/kW difference