Here's a link that compares the GX to the gasoline powered LX and the gasoline powered Civic.
- 2010 Hybrid Civic: $26,510 - $0 tax credit = $26,510
- 2010 Civic GX: $26,050 - $4,000 fed credit - $3,450 OK credit = $18,600
- 2010 Civic LX: $19,715 - $0 tax credit = $19,715
Frankly, I don't know how one could justify the purchase of a hybrid Civic over a Civic LX; much less a Civic GX.
Regarding fuel costs, the hybrid Civic gets an average of 42 mpg vs the GX's 28 mpgge. That's a 50% increase in fuel efficiency. However, the gasoline price per gallon for the hybrid Civic is 100% higher than the CNG fuel per gallon of gas equivalent for the Civic GX... So the Civic GX is thousands of dollars cheaper to purchase than the hybrid Civic and is much cheaper to fuel than the hybrid Civic.