Another way in which Pinterest is an outlier in this list is that its user base skews heavily female (>80% according to one source: https://www.omnicoreagency.com/pinterest-statistics/). I wonder whether some "Moneyball Factor" could be at work, in that this led to it being underpriced for its potential.

Snapchat users also skew somewhat female, but they are also quite young compared to other sites, and "youth" may lead to it being highly priced.

[Being an old dude, I never use either of these]