> No they will charge you for addresses you don't use.

No, that is what they currently do. Starting January 1, 2020, they will charge you for addresses on active instances.

Current:

Static IP address (assigned but unused) $0.010/hr

Starting January 1, they add:

Static and ephemeral IP addresses in use on standard VM instances $0.004/hr

Static and ephemeral IP addresses in use on preemptible VM instances $0.002/hr