I think it is important to keep in mind that - while the relative difference in tax rates might matter - the absolute difference is key as well. If, say, a sword has an item value of 1000, then the tax difference between green and red would be 200 silver. What will matter is how much effort it is to get those 200 silver: do I have to kill 20 mobs for it? Or just 1? How long would it take me?
It is those absolute differences that become extremely important given that the overall silver cost of crafting is much lower now. If, for example, that extra silver would equate to on average 3 extra mobs to kill, would it not be worth it given that you can then craft in absolute safety? If, on the other hand, it would equate to killing another another 100 mobs (for the sake of the argument) then it might not be worth it at all.
Again, we will see how this plays out during the upcoming test and take it from there. See my post above.
All the best,