"Average" is probably not the right word, but maybe the author is referring to full-on water baths, not immersion circulators? the Sous Vide Supreme Demi is between $300 and $350. A Fusionchef water bath is up to $2000.
I'll use the Anova (which I got for free, I wouldn't have bought it otherwise) if I need a very large bulk batch of something that I'm not worried about keeping at a precise temperature, but the SVS fits me a lot better otherwise.