I don't understand why you would have a crown sale on mounts that can be bought with coins. That doesn't make any sense to me at all.
You should be having the crown sale on the mounts that cannot be bought with gold, such at the new Arcus mount (the mount that you didn't even bother spending time creating a new model for, instead you used the flying carpet model).
In case you didn't know, they have an event call Mount-a-Palooza. They bring back retired mounts that were originally bought with gold and they do put crown mounts on sale. Hope this post gives you some insight.