Well there's an explanation that is obvious but numbers help: ^^that's a tiny shroom. Cultivars I know it's probably 0.5g each single shroom.
That's not a jibe at @user's penis size, I don't know if User has a penis. I was thinking, having honestly for reals taken "Edible mushroom cultivation" through the plant pathology dept back in the day, it is fairly easy to adjust the stalk length (and cap size, etc.), Makes no difference for psychoactives of interest, but from a marketing standpoint, I bet there's definitely a bimodal shift to tiny v. long.
Then again, I don't know if that's really a money maker for anyone in the first place. (Psychedelics are meant to be free, IMO.)
(I'm not totally nuts: a "Meaty Portobello" is just another agaricus bisporus. All they do is take a calculated number of the regular pizza mushroom boxes, thin them out, and turn the lights on. With enoki they shade the caps but bunch the stalks or something, so long thin and pale.)