Earning from mobile app development can involve various revenue streams depending on the app’s purpose, features, target audience, and overall strategy of the developer or the company behind the app. Below are a few common ways through which earnings can be generated:

1. **Paid Apps**: Charging users a one-time fee to download and install the app. The price can range from less than a dollar to several dollars depending on the value proposition of the app.

2. **In-App Purchases**: Offering additional content, features, or subscriptions within the app. This can be anything from premium content, additional levels in a game, or unlocking special features.

3. **Subscriptions**: Charging a recurring fee for ongoing access to content or services. This model has become popular with streaming services, productivity apps, and health and fitness apps.

4. **Freemium Model**: Providing the app for free but offering premium features that users can purchase. This model is common in game apps and service-oriented apps.

5. **Advertising**: Monetizing the app through ads. Ad revenue can come from various formats such as banner ads, interstitial ads, video ads, or native ads and can be based on clicks (CPC), impressions (CPM), or conversions (CPA).

6. **Sponsorship**: Teaming up with brands to include their content or service within the app, which can be a source of revenue, especially if the app has a specific niche audience.

7. **Data Monetization**: Collecting and analyzing user data, then selling it to third parties. This must be done with care to avoid privacy violations and ensure compliance with data protection laws like GDPR or CCPA.

8. **Affiliate Marketing**: Earning commissions by promoting other companies’ products or services within the app.

9. **Merchandising**: Selling merchandise or physical goods related to the app, which can be particularly effective for popular games or apps with a strong brand or fan base.

10. **Licensing**: If the app has proprietary technology or content, licensing it to other developers or firms can be a source of income.

11. **White Labeling**: Developing a generic app and allowing other companies to brand it as their own for a fee.

12. **Consulting and Custom Development**: Offering expertise and custom app development services to clients, which can be a significant earning for mobile app developers or studios.

13. **Crowdfunding**: Receiving funds from users or investors through platforms like Kickstarter or Indiegogo to develop the app, usually in exchange for early access, perks, or equity.

14. **Exit Strategy**: Building and growing an app with the intention of selling it to a larger company for a profit.

When considering how to earn from app development, it is crucial to understand the target market, competitive landscape, and what monetization strategy aligns best with the app’s user experience. Also, it’s important to note that app development and maintenance can be costly, and not all apps will be successful in generating significant revenue. As such, market research and a solid business plan are essential components of a successful app development project.