Avoiding creating duplicate Contacts in Marketing Cloud when using Sales Cloud records

Generally speaking, we create Automations that do a Query/Extract/Import to All Subscribers for any email address that's associated with an unsubscribed Subscriber Key. This obviously doesn't prevent the duplication, but it honors the unsubscribes.

Clients unknowingly create duplicate subscribers all the time, but this is an inherent duplication in the platform and is tied to billing.

I feel as though the battle against keeping Contact counts down from a billing perspective is a losing battle.

The fact that all subscriber-based synchronized Data Extensions will count towards the total is alone a huge burden. Converted Leads are never removed from Salesforce, so even in your scenario if were able to remove the original Lead instance from Marketing Cloud (and somehow remove it entirely), it would still count towards the Contact total if we were synchronizing the Lead object.

My main concern is always on unsubscribes: Making sure that once a Lead is converted their new instance new Contact instance will have the same Email Opt-Out status, ensuring if they unsubscribe from an old email sent to their Lead instance they are unsubscribed again as a Contact, etc. The Lead synchronized object holds a converted status so we can always be sure of when Leads are converted, and we can filter from that information to only send to unconverted ones.

Anyway just sharing my thoughts - would definitely also love to hear if anybody has their own tricks for this