After expenses, the net gate receipts are split - 12.5% to the four clubs involved in the semis and 50% to a pool account which I believe is divided amongst all of the teams in the league depending on where they finished the season. https://www.efl.com/clubs-and-competitions/sky-bet-play-offs/playoff-rules--regulations/
I didn't even think about this as I assumed it would just be like a normal home game! But what a joke that is, it will cost more to open the SOL (policing, stewards etc..) yet we get the se money out of it as the rest so will make less despite most the money coming from our fans!