The dragon's biology kinda doesn't make sense. If the master dragon doesn't mate more than once in their life, then the dragons are actually dying species.
I think the reward makes a certain level of sense. This is one of the only sources of fresh dragons in the entire world. People would obviously try to steal the egg to either ransom it back or have their own dragon producing factory. Given the usefulness of dragons in this world, it might actually be more valuable than the life of a princess