It's a low cost airline so what do you expect. They're making very little profit on the tickets and try to make it up in other ways such as food sales and yes, excess baggage.
Regular airlines often turn a blind eye to an extra few kilos, but they make up for it in the ticket price. Depending on what you're carrying it can be cheaper to use the dustbin than pay excess charges. Paper is particularly heavy,so take as little as possible. Do you need a full bottle of shampoo for a three day trip ? Buy those small toiletary containers from luggage shops. Read the regulations regarding hand luggage, quite often it's one bag + camera, umbrella, reading material, overcoat. So you would be better of carrying these seperately and keeping the weight of the bag down.
Low cost airlines are good as long as you understand and follow their rules, and don't expect them to be the same as a full service operator.