If you're already deployed inside Kubernetes or similar, Vault is Just Another Pod that is running, with HA and everything. You might not even need to add to your resource pool that is already provisioned. As for your backend, S3 is a great choice if you can tolerate no-HA, or DynamoDB if not.
Point being: if you're using a modern stack, you can use modern tools. If you're stuck on a legacy stack, you use legacy tools, and that appears to be who AWS is building for nowadays. Legacy tools, value-based pricing instead of cost-based, charge a boatload, buzzword heaven, sell it to the enterprise, rinse repeat.
The HSM component is the only part here that appears to be worth the price. Azure's competing product is a LOT cheaper, except that their HSM-generated keys are more expensive. Which naturally means, Azure is cost-based pricing, whereas AWS is value-based pricing.
Point being: if you're using a modern stack, you can use modern tools. If you're stuck on a legacy stack, you use legacy tools, and that appears to be who AWS is building for nowadays. Legacy tools, value-based pricing instead of cost-based, charge a boatload, buzzword heaven, sell it to the enterprise, rinse repeat.
The HSM component is the only part here that appears to be worth the price. Azure's competing product is a LOT cheaper, except that their HSM-generated keys are more expensive. Which naturally means, Azure is cost-based pricing, whereas AWS is value-based pricing.