I'm glad someone pointed out that making an offer is not illegally poaching.
Just to provide a ballpark sense of what a top group can make, the money is all mainly in concert tickets and merchandising sales. For BP in roughly one year -

"In just 40 out of 60 shows, the group has already gathered a revenue of $163,832,685. The group's sold-out world tour started in October 2022 and will continue to Q3 2023, with a total of 60 shows."
and this is just for tickets. Merchandise sold is about the same as ticket sales.
This is why Kakao is willing to buy 40% of SM for Aespa and NCT for $1 billion US.
Would Fifty Fifty likely do such big numbers. No, but if successful they would be very profitable, because in the west celebs can do really well with licensed products, and they can sing, so it means they could perform till 35-40+ years old each.