So I just did several calculations here. It really isn't bad if you have just a couple tanks. I have tenners, and have experience right now with SS gh/kh which breaks down to roughly .06 per wc. MK breaks down to roughly .15 per wc. In just a few tanks, the cost isn't much of a difference- plus, liquid is much better in my opinion than powder which tends to clump up or be inaccurate at times.
However since I have more than one tank (60+), $173 per year vs $432 per year make a bit of a difference in my budget. Wish I could focus on TB/Pinto tanks and make it all worth it. My temp flux is just too great in my aqua room.