A key belongs to one team, many keys can share one plan
Use separate keys for apps and environments while keeping their usage, rate limit, and billing under one team.
Staging and production need separate credentials, but they usually don't need separate subscriptions. They're environments of the same project, and whoever pays for that project probably wants to see the usage together.
In ParseAPI, a key belongs to one team. You can create a key named Staging and another named Production, and both use that team's plan. Their requests count toward the same allowance and share the same rate limit.
The separation is still useful. You can revoke the staging key without interrupting production, or give a new app its own key so you can tell its traffic apart in the dashboard. Creating another key doesn't create another bill or another pool of included requests.
A separate team is for separate billing, such as another business. A separate key is for a project, an app, or an environment within that team.
That is the distinction I want people to make when they're setting things up. You shouldn't have to decide how many subscriptions you need just because you have a staging server. Give it a name on the Keys page and let the team's plan cover the work.