Cash Bonus is a multiplier to the cash you earn from all sources (including wave bonus). It consists of both a workshop stat and a lab.
Consists of 149 levels, with a total of 2.49x multiplier at maximum level. The Cash Bonus workshop enhancement applies an additional multiplier to Cash Bonus.
The Cash Bonus lab increases the increments of each workshop upgrade and raises the maximum workshop value. You unlock this lab in Milestones by unlocking labs, which you do by reaching Tier 1 wave 30.
The Cash Card increases the cash bonus and is multiplied with the respective lab bonus.
The Cash Bonus Perk is a standard perk that gives 1.15x to all cash bonuses.