The word on the street was that RSL boys were booted from ECNL for something "dodgy" that I wouldn't say. They leveraged it for 2 EA boys teams. I can guarantee you that the boys/parent do miss ECNL given that they are in a crap EA desert mountain or whatever league. That said, boys ECNL has a few strong teams, but generally boys ECNL is not strong. The ECNL teams are regularly beaten by non letter league teams in tournament play. The few teams that I know the make up of locally wouldn't win the local league and are still competitive in a travel league!!
Just as girls ECNL is the place to be, MLS Next is the place to be for boys. That's not even debatable. If ECNL mandates clubs drop MLS Next for boys ECNL or lose girls, they will be strengthening the GA, because plenty of clubs will pick MLS.
From an AZ perspective, the boys teams way outnumber the girls. Boys are attracted because of the promised "pathway", which includes ECNL and MLS Next - there are a lot more $ generated from the boys. I would say that the girls parents likely pay out a lot more money as there seems to be more travel on the girls side (league games & tournaments) than on the boys.
In both instances, parents are parted with their hard earned dollars with relative ease though.
As for generating revenue, there are way more scholarships from the clubs for boys. I don't know if they even bother on the girls side as that's become an absolute pay to play system. If they want the extremely talents boys, then they need to scholarship, as many of them come from poorer families who won't and can't pay.