The only explanation that is viable is because other breeders charge that amount,it's ok for others to follow suit and cash in on colour.

My bitch an other dogs have been bred from the same lines as this stud dog,that does not make them unique,is the dog shown?A stud fee of £400 is I think OTT in a dog that if he is shown,hasn't done anything in the ring,you can use a CH dog with similar lines for less than that.

What are you hoping he can add,in terms of quality?