feat: Document new synthetic default dataset item event (#2007)

resolves: apify/apify-core#23408

Author: michael-apify

sources/platform/actors/publishing/monetize/index.mdx

@@ -38,7 +38,7 @@ The following table compares the two main pricing models available for monetizin
 | Marketing boost         | Standard visibility           | Standard visibility           | Priority store placement      |
 | Commission opportunities| Standard 20%                  | Standard 20%                  | Promotional 0% periods (until 01/11/2025)       |
 | Custom event billing    | Not available                 | Not available                 | ✅ Charge for any event       |
-| Per-result billing      | Not available                 | ✅ Charge per dataset item    | Optional (via event)          |
+| Per-result billing      | Not available                 | ✅ Charge per dataset item    | Optional (via event; automatic via `apify-default-dataset-item`) |
 
 ## Setting up monetization
 

sources/platform/actors/publishing/monetize/pay_per_event.mdx

@@ -108,7 +108,7 @@ async def charge_for_api_product_detail():
 
 async def main():
     await Actor.init()
-    
+
     # API call, or any other logic that you want to charge for
 
     charge_result = await charge_for_api_product_detail()
@@ -136,7 +136,7 @@ Use our [SDKs](/sdk) (JS and, Python or use [`apify actor charge`](/cli/docs/nex
 
 ### Use synthetic start event `apify-actor-start`
 
-:::info Synthetic Actor recommended
+:::info Synthetic Actor start event recommended
 
 We recommend using the synthetic Actor start event in PPE Actors. It benefits both you and your users.
 
@@ -179,13 +179,26 @@ Your Actor might already have a start event defined, such as `actor-start` or an
 
 If you want to use the synthetic start event, remove the existing start event from your Actor and add the synthetic start event in Apify Console in the **Publication** tab.
 
+### Use synthetic default dataset item event `apify-default-dataset-item`
+
+The `apify-default-dataset-item` synthetic event charges users for each item written to the run's default dataset. It lets you align PPE pricing with per-result use cases without adding charging code to your Actor.
+
+This event simplifies migration from pay-per-result (PPR) Actors to the pay-per-event (PPE) model. No code changes are required.
+
+#### How the synthetic default dataset item event works
+
+- Apify automatically charges this event whenever your Actor writes an item to the default dataset (for example, when using `Actor.pushData`).
+- No code changes are required to charge this event.
+- You can remove the event in Apify Console if you don't want automatic charging for default dataset items. If you remove it, default dataset writes will no longer be charged automatically.
+- The event applies only to the default dataset of the run. Writes to other (non-default) datasets are not charged by this synthetic event.
+
 ### Set memory limits
 
 Set memory limits using `minMemoryMbytes` and `maxMemoryMbytes` in your [`actor.json`](https://docs.apify.com/platform/actors/development/actor-definition/actor-json) file to control platform usage costs.
 
 ```json
 {
-    "actorSpecification": 1, 
+    "actorSpecification": 1,
     "name": "name-of-my-scraper",
     "version": "0.0",
     "minMemoryMbytes": 512,
@@ -213,15 +226,15 @@ import { Actor } from 'apify';
 
 const processUrl = async (url) => {
   const response = await fetch(url);
-    
+
   if (response.status === 404) {
     // Charge for the work done and return error item in one call
     await Actor.pushData({
       url: url,
       error: "404",
       errorMessage: "Page not found"
     }, 'scraped-result');
-    
+
     return;
   }
 
@@ -232,7 +245,7 @@ await Actor.init();
 
 const input = await Actor.getInput();
 const { urls } = input;
-  
+
 for (const url of urls) {
   await processUrl(url);
 }
@@ -251,30 +264,30 @@ import requests
 
 async def process_url(url):
     response = requests.get(url)
-    
+
     if response.status_code == 404:
       # Charge for the work done and return error item in one call
       await Actor.push_data({
           'url': url,
           'error': '404',
           'errorMessage': 'Page not found'
       }, 'scraped-result')
-        
+
       return
 
     # Rest of the process_url function
 
 async def main():
     await Actor.init()
-    
+
     input_data = await Actor.get_input()
     urls = input_data.get('urls', [])
-    
+
     for url in urls:
         await process_url(url)
-    
+
     # Rest of the Actor logic
-    
+
     await Actor.exit()
 ```
 
@@ -294,7 +307,7 @@ However, we acknowledge that some events don't produce tangible results (such as
 Examples:
 
 - _`post` event_: Each charge adds one social media post to the dataset
-- _`profile` event_: Each charge adds one user profile to the dataset  
+- _`profile` event_: Each charge adds one user profile to the dataset
 - _`processed-image` event_: Each charge adds one processed image to the dataset
 - _`ai-analysis` event_: Each charge processes one document through an AI workflow (no tangible output, but valuable processing)