JoshuaDavies-4268, As SaiKishor-MSFT mentioned, you can leverage Azure Pricing calculator to get a cost estimate for running Azure resources.
For App Service WebApp, for the production workloads it’s recommended to leverage the dedicated Standard pricing tier or above.
While the price goes up for higher tiers, it also gives you more memory and storage and higher-performing hardware, giving you higher app density per compute instance.
Kindly checkout this doc for detailed insights on: Plan and manage costs for Azure App Service
Depending on your needs you will have purchase a separate database tier.
You can either leverage serverless Azure SQL server or General Purpose PostgreSQL flexible server - You can start with lower tier database and then scale these services up or down to fit your needs.
Reservation and Cost Optimization:
Additionally, you can get a discount of up to 72 percent* over pay-as-you-go pricing on Azure services when you prepay for a one- or three-year term with reservation pricing.
Checkout this doc for more info.
With Azure Cost Management features, you can explore, analyze, budget, and optimize costs for your subscription.
Explore and analyze costs with cost analysis
[[Azure pricing calculator]