Meta terminology

ARPU

average revenue per user

Revenue divided by active users. The source document states that older users have much higher ARPU than younger ones, yet acquiring people young still maximises lifetime value, because "[r]etention overpowers the fact that ARPU is lower for young people."

Sources

Internal documentMarket Landscape Review: Teen Opportunity Cost and Lifetime Value6 Sep 2018

Internal documentMarket Landscape Review9 Aug 2018