Earlier quoted context omitted.
(I have no idea what your infra is so don’t take this as prescriptive) My feeling is that for the average company operating in a (single) cloud, there’s no reason to use vault when you can just used AWS Secret Manager or the equivalent in azure or GCE and not have to worry about fucking Etcd quorums and so forth. Just make simple api calls with the IAM creds you already have.
Caveat: the HCP hosted vault is reasonably priced and works well. However, strong agree on using your home cloud's service. We used Vault with Heroku and were happy.
HCP hosted Vault starts at ~$1200/month, you'd have to use a metric shit ton of secrets in AWS or GCP to come close to that amount. Yes Vault does more than just secrets, but claiming anything HC sells as reasonably priced is a reach.