Well, it's a bond. You will get every single € back if you chose to stay for at least three years. And this is only the case if you come without a 787 or 777 rating. In case you come with an active 777 rating, you won't have a bond at all.
Same case for more or less any low cost carrier in Europe. But I guess bringbackthe80s and Daddy Fantastic are well set up with legacy contracts, so why even try to shoot the messenger?