I thought powdered formula was supposed to be cheaper than concentrate

My son is 7 months old and i been giving him powdered formula his whole life so far... besides the last 2 days i had some concentrate.. he is on good start formula... but i waa always under the impression powdeeed was cheaper ultimately... but the reason i have concentrate on hand as well right now is the fact it was old packaging for the brand so it was on clearance pricing so i picked some up. But anyways... a big container of good start lasts my son 8 days.... from what i xan see of the concentrate for what he drinks he drinks one of those little boxes of concencentrate in the box of formula a day it comes with 12 boxes there for 12 days worth... both the big powdered container and concentrate is the same 47.99 to buy or (42.99 when i buy on sale plus i use coupons and buy at shoppers to earn shopper points ultimately costing me about $25 for either or) if i would have known concentrate would have lasted me longer instead of powdered i couls have saved aprpx $300 on his formula!. I do prefer powdered tho for when i go out as its easy to fill bottles with water and mix powder in when needed since he will take room temp. But anyways why havent anyome told me it was cheaper????