Do you know how much charging costs?

My EV journey may be slightly delayed, but I’ve still been checking out things like charging in preparation. This is probably a dumb question – but why’s it so hard to find out how much a charge will actually cost? We have huge signs by petrol stations so we can see the price before we drive up; but for chargers you seem to have to actually push buttons on the unit itself and then the price seems to vary wildly. Or is this a “non problem” for those with EVs who know the score?