Money, also known as Cash, is the main currency in the Bloons Tower Defense series. You use money to buy towers, upgrades, and other special items. In Bloons TD 4 and Bloons TD 5, the player can buy a Premium Upgrade called Double Cash Mode, which gives the player twice the money for each bloon popped and also starts the player out with twice the regular amount. You can't get money in Deflation Mode. It is unconfirmed that Money has a "maximum limit", as the maximum limit could be somewhere beyond 1,500,000+, if the player has that amount of money, money could only be obtained via Abilities (such as Supply Drop Ability), and not from pops.