I've noticed some websites have implementations that include the same server call (data, structure, etc) going to two report suites. The AEC debugger seems to count the duplicate server calls as just one.
How is something like this configured in a best practice? Just comma separated report suites in Launch?
Also, is there a cost to this? As in, does this count as two billed server calls or one?
Generally companies send data for specific pages, countries, languages or during data migration to a secondary report suite with all data to global report suite. It helpes to separate data access for different groups based or to avoid data loss during migration. Today with Virtual report suite you can do the same without sending call to secondary report suite. How? Limitations etc. is well explained here https://docs.adobe.com/help/en/analytics/components/virtual-report-suites/vrs-considerations.html
Still if you need to use multi report suite tagging, can certainly do by adding multiple report suite in launch by using comma separated list.
multi suite tagging is going to cost you for primary and secondary server calls, you can check with your adobe account manager or support team to get details on this.