Maybe not at first, but it will come to a point when it will drop. Since using the Trade hub itself is an easier way to trade, not having to sit and spam "trade" as you did before 24/7.
And only time you'll encounter less "profit" whould be at the start of the change aka the patch. When the system is completely new and market itself is in flux. But that's the diffrence between a good player and a bad is to knowing when and how to play the market.
Also wanna add that the tax itself will help against anyone who are trying to flux the market, making it harder to undercut people without any losses. Like i said before, its there for a reason.