Matcha water?

First of all, why is matcha water a thing? Do people really love matcha that much? And also, what do you typically charge it as when they order it? People will usually order it as "___ ice water with __ scoops of matcha" or quite literally matcha water, and when I first heard this order I rung it up as water with matcha scoops which will never be more than whatever the 80 cent charge for a matcha times however many scoops they requested. I was promptly told by another barista that you have to ring it up as a custom iced tea which is around $3.50 for grande if I recall correctly? which is significantly more than the previous way of ringing it up. Is the latter correct? i know it's not one of the cheaper ingredients but does it really cost starbucks that much to make it?