That sounds off. It sounds break even at best and I'd be surprised if they didn't take a small loss at those numbers. If we assume they get packs at $2 cost that leaves $5 profit for 4th-8th after payout and product. $2 is about right IIRC I think it might be as low as $1.80 a pack depending but I don't think it's lower. That would be absolutely insane payout unless it's some special event. If it's a store that does a business via food and drinks and shit I could see it but they would have to be next to a military base with a ton of magic playing baby military who throw money around like Saudi Princes (which is depressingly likely).
The store I play at in AR has stupid high payouts for things like pre-releases and better than anywhere else I've ever played for average events but they don't come close to touching that.