Azure Key Vault is an Azure service to safeguard your keys and secrets from all forms of threats and errors for all its users who are deployed in both Azure and non-Azure environments. Azure Key Vault services are very cheap to deploy and comes in two different terms, Standard and Premium. Now, pricing for different operations like Secrets, Certificate Operations come at $0.03/10,000 transactions, and if you apply for renewal, it will cost you $3 per renewal request. Whereas the pricing is the same for Software-protected keys (RSA 2048-bit keys) but different for advanced key types, like (RSA 3072, RSA 4096, ECC, etc.) which will cost you $0.15/10,000 transactions.
And if you are going for HSM-protected keys, RSA 2048-bit keys will cost you $1 per key per month plus $0.03/10,000 transactions etc. If you wish to dive deep into Azure, check out the AZ-500 online training certification from Intellipaat to get yourself trained and certified, which will help you in getting Azure Certified. Check out the following YouTube video on Azure Tutorial for beginners.