Getting non-BS info on tea in the west has been somewhat dubious ime. The “ceremonial” grade designation is mostly a western marketing thing afaict, but I take it to mean quality that is high enough for koicha, the thick paste preparation style. So the problem here is you have to use several grams of powder to just a few ounces of water to get that consistency, and that can get costly.
I haven’t ordered matcha in years but think this was supposed to be a reputable source? I’m borrowing some tips from the coffee universe here: they provide a farm/source name, it’s single cultivar, and they have some details on selection/processing.
@Ikioi might have better insight about where to buy from. Like, it wouldn’t surprise me at all if the best of the best can only be found on non-English sites.