I agree that 150k is a bit silly but I think majority of the cost comes from the fact it has a day cool down on both the mats, the one that requires ghost iron needs a good amount of ghost iron and then you have to get along with something around 360 trillium ore or so, get that put into trillium bars and then into living steel. While 150k sounds a bit steep I feel like it could still go pretty high considering the rest of the crafted mounts are more expensive.