A Prius is 46 combined, the Civic is only 32 combined (as per fuelly). The base Civic uses 50% more fuel than a Prius, I'd hardly consider that "nominal", that's the difference between a 6.2L V8 powered Corvette (22 combined on fuelly) and a Civic.
Another way to look at it is, $2/gallon gas in a Prius is $3/gallon in a Civic.
Sure, but, as (s)he said, (s)he drives 5-10K miles / year. For 10K miles, that's a difference of less than 100 gallons of gas per year, meaning less than $400 / year in gas for the Civic vs the Prius. ~$1 / day probably isn't going to drive behavior change or a willingness to spend more for an otherwise-inferior car.
A Prius is 46 combined, the Civic is only 32 combined (as per fuelly). The base Civic uses 50% more fuel than a Prius, I'd hardly consider that "nominal", that's the difference between a 6.2L V8 powered Corvette (22 combined on fuelly) and a Civic.
Another way to look at it is, $2/gallon gas in a Prius is $3/gallon in a Civic.