Meanwhile, Facebook's ARPU in Europe is ~$50/user/year [1], so they're roughly $40 ahead per claimant after this lawsuit. Just a cost of doing business...
Revenue is not the same as profit, from the source you quoted the ARPU in Europe for 2016 (period lawsuit starts) is half of what it is in 2020, also it's closer to 15$ since GBP is worth more than USD.
Highly doubt this would be in the "cost of doing business category"
Highly doubt this would be in the "cost of doing business category"