You could just as easily say that sparkling water is a mistake when you can get tap water and seltzer tablets for cheaper, or that Coca Cola is a mistake when you can get sugar and caramel and water and mix them yourself.
Asparagus water sounds awful to me. But so does a lot of stuff that normal people buy, things that are not strictly necessary for survival but people like for some reason. This article is just "hey Whole Foods is expensive and trendy, has anyone noticed this?"