I love to watch Borean Leather on my server. The market floods from time to time and you can catch stacks and stacks of it way under value.
First lets define vender value for Borean Leather. I never vender it, but if my markets crash I can still turn a profit by vendering it. Frostscale Leggings take 12 pieces and vender for 5g35s64c. That works out to 44.6 silver a leather or 8.93g a stack. I see it sell for as low as 30 silver on my server. So daily I purchase all leather under 41 silver. But lets look at the other ways to make gold off of it.
First is to check the conversion to Heavy Borean Leather. That takes 6 leather a piece. At 41 silver anything I sell over 2.58G is profit. I sold several stacks at 4.3G each last night. Thats higher then the norm. 3.5G is more commonly what I sell it at. But thats still a good profit.
Heavy Borean Armor Kit is another item that sells well for me. It takes 4 heavy leather (24 borean leather) at a cost of 9.8G and sells for 15G or more.
And an item I mentioned previously is Dark Iceborne Leggings. It takes 4 heavy leather (24 borean leather) and 1/2 an eternal shadow at a cost of 11.3G and sells for 15G or more as a Dream Shard.
With these three options I can buy every piece of borean leather that I see and know that I have several channels to push it onto the market. If I keep buying up all the supply, then it also prevents anyone from moving into those markets. This is one item on my daily snatch list.