I'm referring to the cost of the wiring, not raw copper stock price. Also, I mean the cost of the wire from the breaker panel to the HVAC unit. On average, I'd assume that the wire run is at least 50 feet. 100 feet wouldn't be unusual. 100 feet of single-wire 10 gauge THHN (enough to run most HVAC units here) would be ~$60. That also doesn't include any additional cost by upsizing certain things (conduit) that may add.

To note, as mentioned, copper is not the only cost here. You also need another pole to your breaker, which adds cost. Plus busbar upgrades. And more.