Two groups with some members are in both groups

We have one management but two groups for two companies and some members are in both groups. Should i buy plans for these overlapping members twice?

Example:
Group1 with 9 members (6 are different and 3 are in Group2 also)
Group2 with 9 members (6 are different and 3 are in Group1 also)
It seems we have to pay $432 * 2 = $864 but we have only 16 developer so we should pay $768 only.

Thank you.