REUTERS/Edgar Su Apple is locked in an escalating standoff with app developers who are upset that Apple takes a commission of up to 30% from all in-app purchases. This week, the creators of a new email app called Hey publicly slammed Apple as "gangsters" after Apple rejected Hey from the App Store. Hey creators said Apple was forcing it to recategorize its $99 annual subscription fee as an in-app purchase in order to take a cut of the profits. Apple doubled down in an email to Hey creators Thursday, saying the app would remain banned from the App Store until Hey reclassifies its $99 subscription fee as an in-app purchase.