Jackpot fee
A deduction from the pot into the room's prize pool, on top of rake. Not covered by rakeback; counted as a separate line in the sessions.
The jackpot fee is a second commission from the same pot. Rake goes to the room, the jackpot fee to a prize pool that later pays for rare hands and random drops. From a $45 pot in session 9 the room removed $2.17 of rake and $1.50 of jackpot fee: the second commission was two thirds of the first.
The main difference: rakeback does not apply to the jackpot fee. That is why in the sessions the two commissions are never added into one figure, although both are taken in the same second. Over fifteen sessions the rake is $267 and the jackpot fee $72, so the real commission is 27% larger than the one the refund is counted from.
Something comes back: over nine sessions the pool paid out $70 in «Cash Drop», random drops at the table. Against $1,371 of total commission from the tables I sat at, that is five percent, and it goes not to whoever paid the most but to whoever it fell to.
The same in business
A jackpot fee is a charge that is not called a commission and therefore never enters the negotiation about commission: payment processing on top of the marketplace fee, mandatory advertising, promotion charges. The discount is given on the figure under discussion; the one not under discussion grows.
The whole hand is in session 9: “If you get to choose, be the marketplace, not one of its users”.
The other terms are in the glossary.