Probably more than you'd expect. They have two levels of subscriptions [1][2]. XTRA is $19.99 per month and Unlimited is $39.99 so potentially the revenue per hookup could be pretty high, at least as far as per user app revenue goes, assuming a reasonable subscription rate.
[1] https://help.grindr.com/hc/en-us/articles/1500008656241-Grin...
[2] https://help.grindr.com/hc/en-us/articles/1500008656741-Grin...