If it was so simple as service -> $$$, they should be paying up the referees, which is the only task that requires rarely found scientific skills.

I seriously can't see how editing, typesetting and hosting can host that much, or can make them a respectable journal. No-name journals (for which top scientists don't referee) have that too.

BTW, Americal Physical Society journals don't even do that and outsource typesetting and editing.