1. Go to your App Store Connect account.
2. Select your app from the My apps section.
3. Go to In-app purchases and Manage.
4. Select the product you want to edit.
5. Scroll down until the section Subscription prices. Click on the blue add-button (+) next to it and select Plan subscription price change.
6. In this pop-up window, you can select which country will be affected by the change in prices. At the bottom of the pop-up window, select Next.
7. In the new pop-up window, select the price and currency for the app. On the start date, select when the new prices should appear on the app. Then click Next. As stated, the prices will be calculated automatically.
8. In the last pop-window, you can change each price manually. Note that some countries have their currency in dollars while others use their own currency. Then click on Save.