1) Automate app testing
Maintaining a ReactJs App can be costly, but with some strategic planning and automation, you can significantly reduce the cost of maintenance. One of the best ways to keep costs down is by automating app testing. Automated testing ensures that your app is performing as expected with each update and reduces the need for manual testing.
Automated tests can be set up to run on a regular basis or triggered when changes are made to the codebase. With automated tests, you’ll be able to quickly identify any issues that arise and take steps to fix them before they become larger problems. Automated tests also help you ensure that your app’s code is secure and compliant with industry standards.
By automating app testing, you can avoid the costly overhead of manual testing and save money on development and maintenance costs. Automated testing also provides peace of mind knowing that you have an extra layer of protection against any potential issues.

2) Use open-source components
One of the most effective ways to reduce the cost of app maintenance is to make use of open source components. This strategy has several advantages, including reducing development costs, increasing the quality and reliability of your code, and providing access to more features and capabilities.

When building a ReactJs application, there are numerous open source components available for use. These components range from UI elements such as navigation menus and forms to more complex modules like databases and authentication systems. By using these existing components, you can significantly reduce the time and effort it takes to develop and maintain your application.

Furthermore, many of these components are designed to work with the React framework and thus provide a more consistent and reliable experience for users. As they are already tested and trusted by the community, you can also be confident that your app is more secure and stable.

Using open source components is not only cost effective but can also be a great way to speed up the development process. By leveraging existing code, you can focus on customizing your app for the needs of your business, instead of spending time on tedious tasks like designing user interfaces or writing data models.

3) Leverage serverless architecture
If you’re looking for ways to reduce the cost of maintaining your ReactJs app, leveraging serverless architecture is a great place to start. Serverless architecture allows you to break up the components of your application and run them on separate servers. This helps reduce the cost of running, scaling, and maintaining your application since it eliminates the need to manage multiple servers.

Serverless architecture also makes it easier to add new features to your application. Instead of having to deploy new code to multiple servers, you can easily add new functionality with a few lines of code. This makes it easy to quickly and efficiently make changes or add features to your application without the hassle of managing multiple servers.

Additionally, leveraging serverless architecture helps reduce the time and money needed for software updates and bug fixes. Because each component of your application is running independently, only the specific code that needs to be updated needs to be changed. This eliminates the need to manually update all of your servers, saving you time and money.

Overall, leveraging serverless architecture is a great way to reduce the cost of maintaining your ReactJs app. It reduces the need for manual updates, simplifies new feature deployment, and helps keep your costs low.

4) Keep your app simple
App maintenance costs can quickly add up, so it's important to find ways to reduce them. Fortunately, there are a few easy steps you can take to keep your app maintenance costs low. 
1. Keep the App Simple: One of the best ways to reduce app maintenance costs is to keep the app as simple as possible. Complex features may be appealing, but they come with a cost. By reducing the complexity of your app, you can avoid costly repairs and upgrades in the future.

2. Use Third-Party APIs: Third-party APIs can provide many of the same features that your custom code would, but at a fraction of the cost. By leveraging third-party APIs, you can drastically reduce your app maintenance costs while still providing the same level of functionality.

3. Automate Updates and Maintenance: Automating routine updates and maintenance tasks can help reduce your app maintenance costs over time. This will free up time for developers and allow them to focus on more important tasks.

4. Monitor Your App Performance: Regularly monitoring your app performance can help you identify issues early on and minimize their impact on your maintenance costs. You can also use performance metrics to optimize your code and reduce the frequency of costly maintenance tasks.
By following these tips, you can drastically reduce your app maintenance costs and keep your development costs under control.