I think $1500-$3000 seems pretty average for a champion stallion.
You start setting fees at $15,000 you limit your stallions marketability. But, maybe that's the point.
I don't think colour should have anything to do with setting a stallion fee.
But, it's like pricing a horse. You can put whatever price tag you want on it, and it's worth whatever anyone wants to pay. I have my HC stallion set at $1500, but his sire's fee is $5000 (plus importation from Poland, vet, etc).
That's the nice thing about selection! So long as you can find good selection.