Well, I value the female carrier 'so much' because in theory both her and her brother carry the xanthic gene from their father, so assuming it turns out to be a recessive gene (and there's a better than average chance) 25% of every spawn should be xanthic jags. The only problem I have right now is that we don't know at what size they change to xanthic, so it would mean keeping as many as possible to large size until they turn and once they do (if they do) I will have pairs of xanthic jags, which will probably pay for most of the yearly cost of running my fish room by themselves.
I have easily got 150-200 fry growing out right now and Ian has close to 100, so providing the xanthic gene is inherited this way, there's a pretty good chance a xanthic will crop up in that lot.
That's why I value her so much!