Depends on what city you going to, as compared to the US, Europe is a bit expensive. I have been to Uk, Italy and I found it little expensive than back home in LA.
Generally speaking, whether someone is going to get a cheap fare or high fare depends actually on where the person is traveling to, how much you would spend on transportation has to do with how long or short the distance is. This is actually the case with most European countries. Traveling around Europe can be expensive sometimes especially when you are visiting countries with high standard of living.
However, there are so many ways to pay very less for fares when you are embarking on any journey. All you need to have is a calculative mind. If you don't want to spend much on transportation, then you will need to adjust yourself to get used to some certain lifestyles. The cheapest form of transportation in Europe is through land. If you are using land means of transportation, I can guarantee you won't spend much on fares but transportation through air will definitely take a lot of money from.