There's 2 separate issues here. Take Ben Hannant for example. Say Ben gets picked for all 3 origin games this year.
1. He would get a match payment from the ARL for each game he plays (say $15,000 per game). That $45,000 he earns is paid out of the profits of SOO. I don't think that would be included in the Dogs salary cap.
2. In addition to the above, Ben has a clause written into his contract at the Bulldogs that says he will get paid an amount (eg $20,000) by the Dogs if he plays SOO this year. That amount will be included in the Dogs salary cap.