royalties/fees
All the variations and sidebets are subject to royalties/fees.
The owner of, for examples, the Super Sevens, might get $100/mo per table on which the sidebet is in use.
Another add-on might earn $200/mo or $300/mo.
It depends on how much action the bet gets and how much it adds to the casino's bottom line.
With separate games, take the example of Carribean Stud: the owner (ShuffleMaster, Inc.) gets the net on the optional bet plus the monthly rental on the shuffling machine.