On 28.04.2017, Apple announced a change to the available price tiers for in-app purchases and will roll this out in iTunes Connect in the coming days. This means that some pricing tiers can no longer be used in the future. In addition, all existing price tiers will automatically be given a new (higher) retail price. All price levels for single issues ("non-consumables") are affected by the current change. For the time being, there are no changes to the price levels for subscriptions ("subscription with automatic renewal").

Excerpt of the announcement by Apple:

What does this mean for you?

In order for your issues to continue to be sold in the app at the price you want, you will need to manually adjust the price tier for each of your products.

How to change your price tiers in iTunes Connect:

To do this, log in to your iTunes Connect account and open the list of in-app purchases for the app you want.

Select an in-app purchase from the list and open the details page.
In the "Pricing" section, you can define the price for the issue. Select the desired price via the drop-down menu and then save the change. Please note that some of the relevant price levels are only listed at the end of the dropdown menu. (The official list issued by Apple, including all new price levels, can be found as a PDF file attached).

Make this change for all existing in-app purchases.
The new price will be used once Apple releases the changes in the coming days.

Remark:

Once you have set a new price for your issues, please also change the price in Pegasus Workbench under the menu item "Publish" for your individual issues, and in the Google Play Store and Amazon App Store.