You being in a non-CARB state, it may be tough to get dealers to budge more off MSRP than what the Costco discount offers. A quick Truecar check shows that dealers in Las Vegas aren’t offering more than $1,500 as a dealer discount, so the $2k Costco discount may be the best you can get right now.
Assuming average taxes/fees, that $384 quote is probably accurate.
In SoCal, you should be able to get a much higher dealer discount. You won’t receive any additional lease incentives, but the dealer discount could be as much as $4k off MSRP.
If you could find a SoCal dealer to agree to a $4k discount, even including shipping costs, the SoCal Volt would be much cheaper than a local one. Should have no problem finding a SoCal dealer willing to lease a Volt to a NV resident. I believe Keyes Chevy in Van Nuys would be willing, and they have lots of Volts!