1. Add a new team to an account.
2. Add members to an account and add them to the team.
3. Add a new project. Check "Billable" and select "By person rate".
4. Add members to the project. Their hour rates will be inserted to the project.
5. Add additional members to the team of the project. Their hour rates will NOT be inserted to the project.
I have to add rates of new team members in every project manually. It's annoying and, it seems, this is a bug.