As someone who is new to hobbying, I've always fantasized about DUOing with two ladies.
Having said that, usually the fee is just their regular rate x 2 (which from the SP's perspective makes sense)
I know it's a little weird to think about cost/performance when it comes to hobbying but I can't help but to think the cost of duoing is better spent on 2 separate sessions instead
Perhaps it's one of those "once a year celebration" thing? Those who have partake in duos, please share your thoughts, thanks