I have created some collections without the full understanding of the new way product IDs are used with collections. Now that I understand, I went back and changed the IDs in each collection to match my one in-app purchase ID. Now when I goto the products and subscription tab to apply my metering selection per collection, I see the old product ID I originally created. Does it not update in the Products and Subscriptions tab when I change it in the Collection Preferences?
Product IDs are used to determine products that are available for entitlement (there are different ways a user can get entitled e.g. in-app purchase, direct entitlement). Products IDs are assigned to a Collection. Every collection must have a product ID in order to publish the collection. A collection can only have one product ID; however one product ID can be assigned to multiple collections (Think of Collection = Content, Product ID = Entitlement Product)
So, if the scenario you're looking to enable is a user purchasing multiple collections with one purchase/entitlement, then assign the same product ID to each collection that you want to be included in the purchase of that product. If you want to offer individual collections for purchase/entitlement, then assign a unique product ID to each collection.
Metering is set up in Project Settings.
To set metering in your application, go to the DPS Portal > Project Settings > Content (tab). Here you check "Enable Article Preview" and enter the settings for the threshold you want to set. The threshold applies to all content in your application. You can choose the # of articles a non-entitled user can read in a given day, week or month. You can also set the time & timezone when you want the threshold to reset (Note: If you set a weekly threshold, the meter will reset on Monday of your selected time zone. If you set a monthly threshold, the meter will reset on the 1st of the month in your selected time zone)
For Metering / Article preview to work, the articles must be published with the article access state of Metered (Metered is the default article access state. Article Access State is set in Content & Layouts > Content > Article Properties > Article Metadata). The product ID assigned to the collection must be "retail" - not Free. If a collection is assigned a product ID that is set to Free, all articles in that collection will be treated as free.