that's true, but I imagine one platform making such changes...

that's true, but I imagine one platform making such changes shouldn't hurt that much given we use multiple sources/platforms. If the change was significant then the platform will likely lose a lot of their traders which would hurt their bottom line a lot more than HT8's. So it's unlikely they would do something that isn't beneficial for both parties like doubling or tripling the fees. To that point, if I was HT8 I would just add that fee onto the top of the current product's pricing anyway. this will likely reduce sales but if someone is shopping for the same item at a different platform HT8 will just get the sale over there instead.