I loaded up $10 a few years ago just in case I ever needed to pay for a Voice call, and it has dropped a whopping $0.02 from one 23 second outbound international call. It’s great that it’s a free service for domestic calls.
in the spirit of never touching a google product again, I'm planning to use mysudo instead of voice. Might be worth a look? It allows you to create up to 8 identities with different numbers.