Want to create an estimate for a very large scale project

For creating an accurate estimate for a large-scale project using AWS App Runner, you should consider several factors and use multiple tools to ensure precision. Here are some key points to consider:

1. Use the AWS Pricing Calculator: This is your primary tool for creating detailed estimates. It allows you to configure specific services and parameters, including App Runner, and provides a comprehensive cost breakdown.

2. Consider all related services: While App Runner is your main service, think about other AWS services you might need, such as databases, storage, networking, and monitoring tools. Include these in your estimate.

3. Estimate your traffic and usage: Try to accurately predict your API's expected traffic, compute requirements, and scaling needs. This will significantly impact your costs.

4. Account for data transfer: Consider the amount of data your API will transfer in and out of AWS, as this can affect your bill.

5. Plan for different environments: Factor in costs for development, staging, and production environments if applicable.

6. Consider reserved capacity: For large-scale projects, reserved capacity options might offer cost savings over on-demand pricing.

7. Use historical data if available: If you have existing usage data from similar projects or a pilot, use this to inform your estimates.

8. Leverage the enhanced AWS Pricing Calculator: This tool, available in the AWS Billing and Cost Management Console, can provide more accurate estimates by incorporating eligible discounts and allowing you to import historical AWS usage.

9. Create a bill estimate: For very large projects, you can use the bill estimate feature in the Pricing Calculator to generate a complete AWS bill estimate, which includes adjustments for Savings Plans and Reserved Instances.

While the AWS Pricing Calculator is the primary tool for estimates, for a project of this scale, it's highly recommended to engage with AWS directly. You can contact AWS Sales or your account representative to get personalized assistance with your cost estimation. They can provide insights based on similar customer scenarios and help ensure your estimates are as accurate as possible.

Remember that creating an accurate estimate for a very large project can be complex, and it's often an iterative process. Start with your best estimates, then refine them as you gather more information about your specific requirements and usage patterns.
Sources
Create and configure an estimate - AWS Pricing Calculator
Create your personalized cost estimate with the enhanced AWS Pricing Calculator (public preview) | AWS Cloud Financial Management
Creating a bill estimate - AWS Cost Management
Generate an estimate in AWS Pricing Calculator - AWS Pricing Calculator

As a large customer, I would be reaching out to your local AWS Solutions Architect and getting them involved. They may be able to point out costs that you've missed or help with optimising estimated expenditure.