Here's a breakdown of four of the best selling cars in the US and their Hybrid siblings. In all cases I chose the closest trim levels and engine sizes. These numbers were taken from
http://www.fueleconomy.gov/. From what I've read these mileage claims are about 20-25% optimistic. In real world driving owners of these hybrids are seeing roughly 1/5 to 1/4 less gas mileage than the EPA claims.
Make Model Engine Transmission MSRP Tax Credit Mileage City/Hwy Annual Fuel Cost Greenhouse Gas Emissions
Honda Accord LX 6 Cylinder Automatic $25,200 $0 21/30 $1,489 7.7 tons per year
Honda Accord Hybrid w/V6 Automatic $31,090 $1,300 28/35 $1,153 5.9 tons per year
Toyota Camry XLE 4 Cylinder Automatic $24,900 $0 24/33 $1,321 6.7 tons per year
Toyota Camry Hybrid ECVT $26,200 $1,300 40/38 $914 4.8 tons per year
Honda Civic LX 4 Cylinder Automatic $17,760 $0 30/40 $1,082 5.5 tons per year
Honda Civic Hybrid CVT $22,600 $2,100 49/51 $714 3.7 tons per year
Toyota Corolla LE 4 Cylinder Automatic $15,515 $0 30/38 $1,082 5.5 tons per year
Toyota Prius Hybrid ECVT $22,175 $1,575 60/51 $650 3.4 tons per year