This of course applies for Ryanair too, where your bag should weigh a maximum of 15kg. They charge from EUR 15, almost SEK 150, depending on the season.
So you should really travel light, with hand luggage only. The maximum weight for hand luggage with the low cost airlines is usually more than the other air companies, 10kg compared to 8kg. That’s why it’s a good idea to buy a case that’s really light. But remember that Ryanair have maximum measurements of 55x40x20cm, whilst Norwegian and others allow a depth of 23cm!