Hipchat: アカウント内の一部のユーザーのみ Plus にアップグレードする
Can a subset of users in an account upgrade to HipChat Plus?
Users are individual but user accounts are not. Billing and plan level is account wide. For example, in an account (xxx.hipchat.com) there are 62 active users at the moment and if you want to switch to HipChat Plus plan, all users within the account need to upgrade. So to summarize, billing is per group (i.e. account) not per individual users in the account even though the pricing calculated is $2/per month/per user.