Depends on how many secrets you're storing. You can also back Vault with something other than Consul. You can back it with DynamoDB, which would be much cheape

Depends on how many secrets you're storing. You can also back Vault with something other than Consul. You can back it with DynamoDB, which would be much cheaper than managing your own Consul cluster. You can even back it with S3, which would be dirt cheap (cost of the vault instance + a few cents for storage).