Europe is full of airports and Airlines. Specially low-cost and budget Airlines have found their place in Europe. When distances are not that big it is easy to offer very competitive prices. There is also number of flights going to same destination every day. e.g. KLM offers seven flights to Paris from London in normal weekday (klm.com).

picture from google.com

Flying inside the Europe is very easy and effortless, there are lots of carriers offering their services. People are flying more than ever specially with low-cost Airlines. Still low-cost Airlines seems to have more negative feedback than traditional ones, there might be various reasons for that, but usually it is too high expectations. There are always reasons why low-cost Airlines are cheap. It might be because of flying to minor airports or flight ticket will not include luggage etc.