Agreed. I'm almost embarrassed to answer "I'm getting 28-30mpg" when my wife's Civic is getting 34. Sure, the Spyder is faster, but it's also less than a quarter the weight. Even my 1200cc BMWs are getting around 50mpg.
Kinda the same here every time they ask. My BMW gets 50 mpg riding double and thats at 75 mph. loaded for trips. My wife's 1100 Virago gets 48mpg.
I noticed though that the spyder seems to be a lot more effected by the wind than our bikes. You get blown around a lot more. Sometimes you can just feel it trying to push you backwards. Got to be the frontal area is bigger or less arrow dynamic.