The key here is the word "kickback".

kickback - 傭金;回扣, commission
A return of a percentage of a sum of money already received, typically as a result of pressure, coercion, or a secret agreement.

It is the money given to Doc Daneeka by the drug stores, not the other way around.

The original translation is wrong. It should be something like,"...兩個藥店增加了我的回扣費"