ARE YOU FAMILIAR WITH THE TERM "CASH COW"?
Collins English Dictionary describes ‘a product or acquisition that produces a steady flow of cash...’. The slang dictionary (must get me one of those) further describes ‘a dependable source of money; a good investment’. Wikipedia goes on to explain that ‘a “cash cow” is also used sarcastically by sales and business people to describe a customer or organisation that has no control over its spending; quite often used to describe a business where spending is out of proportion to the services or goods received.’ 