Dating companies count a member as a payer if they paid at least once in the period being reported, usually a quarter. Match Group, Bumble and Grindr all publish payer numbers alongside revenue.
Payers matter more than downloads or monthly active members because most dating apps make most of their money from a small share of members. A fall in payers usually shows up in revenue a quarter or two later.
Watch the definition. Some companies report average payers across the quarter, others a figure at the end of it, and treatment of one-off purchases varies. Compare like with like.