I don't know how Google does this "accounting", but have observed the following behavior: From my present location (Thailand), if I use a GV account that was set up from within the continental US, I am not charged for US calls. Possibly, it's because it is an old "grandfathered" account. Using a GV account set up from another country, I pay $0.01/min. Or, you might try connecting through a US-based VPN (with hardware VPN router or Internet Connection Sharing on your PC).
If the above doesn't help, you might try Localphone (most US locations $0.005/min.) or a Betamax provider ($0.003/min. or some "free" calls with complex rules)
http://backsla.sh/betamax . IMO, quality will likely be inferior to GV.
Or, if your usage is heavy, try an "unlimited" provider such as VOIPo or Phonepower.