Every App Store, including Apple App Store and Google Play Store charge a fee on in-app purchases. They take a significant cut of your revenue on any one time and subscription charge in your app, that's how they make money.
Subscription billing is particularly popular these days and both Apple and Google have tried enticing developers with a revenue structure that reduces their commission over time.
What percentage does Apple take from in app purchases?
For one-time purchases Apple charges a 30% fee.
Since 2016, Apple has reduced the fees they charge for subscriptions, but only after 12 months of service.
In the first year of a subscription, Apple takes a 30% cut of your revenue, so you receive 70% of the subscription price at each billing cycle, monthly or annual, minus applicable taxes.
After a year of service, your revenue share increases to 85% of the subscription price, minus applicable taxes, so Apple takes 15% of your revenue.
Update: Want to avoid Apple's 30% App Store fee? Apple is changing their rules about what's allowed and what not. It's now allowed for you to contact app users about payment options outside of the app. You can't link to other payment options yet, but you might be able soon.
All subscriptions on all Apple platforms are eligible, including paid introductory periods (pay as you go, pay up front). The period calculation excludes free trials and bonus periods. Upgrades, downgrades, or crossgrades between subscriptions in the same group don't affect the one year calculation. A move to a subscription in a different group resets the count of days.
What percentage does Google take from in app purchases?
Like for one-time purchases, Google's revenue share on subscriptions is 30% of the price. You receive 70% of the payment.
Like for Apple, Google's cut on your revenue for subscriptions decreases to 15% after a year, so you'll retain 85% of the revenue after 12 months.
Subscribers within a grace period, or that recover from an account hold, grace period, pause, or subscription restore still count. Same for people that sign up at introductory pricing, those that upgrade or downgrade or re-sign up within two months of cancelling. What doesn't count towards the 12 months are free trials, refunded purchases and any time while the account is on hold.
You don't get your money immediately when you sell a subscription. Google pays out just a few days after the end of the month, with no minimum.
Apple makes payments 30 days following the end of each monthly period. To receive payment, you must have provided all required banking and tax information and meet a minimum threshold, ranging from 10USD to 150USD.