ATM Fees Abroad: Asking the Monzo Community to decide pricing

The £16 is if everyone pays, not optionally, and might rise or fall.
They took the total fee / active users. 85% of the total is from 13% users.
So can you try the maths again, 13% of 401661 users costs £5.4 million a year (401k * £16 * 85%).