$100-$110 to fill up, I fill up 3-4 times a week, multiplied by 4.2, leaves me somewhere between $1,250 and $1,850/month; them we have the wife's 70+ mile work commute /day - $1,200/month seems very reasonable to me.
Holy cow, man. Unless you're in the delivery business or a trucker, that's an insane amount of fuel consumption. My wife and I have two vehicles, and live an hour from anywhere. Yet we don't consume more than 700 gallons of fuel between us in a year. Haven't for the past nine years. And a lot of that is "recreational" too. My wife visiting family, or running around with the kids. I personally consume about 265 gallons of fuel/year. And if I use the middle of your range and assume $4/gallon for gas (round number, to make the math easier), that's 375 gallons/month of fuel consumption...just for you! Excluding your wife, from the sounds of it.
So the earlier question was actually reasonable then: Do you drive a tank?!
Even if I drive my 5.9L 4wd "tank" 100 miles per day I'm not near $1200/month. 
If we're talking household, sure. I have 6 cars, 4 of which are driven daily.
I drive a 5.9L 4wd, and I'm close to that..

But yes, we were talking about a household, not an individual vehicle. You can't measure what your family spends on food if you only count what you spend on milk..An average of 100 miles a day is probably high if you live in city and have a desk job, but is probably low if you own a service buisness.
- primary vehicle (many variables here, depending on who drives the most, husband or wife, and what each of them drive)
100 miles per day @ 15 miles per gallon @ $4 per gallon = $186.66 per week = $9706.66 per year
- Secondary vehicle
50 miles per day @ 22 miles per gallon @ $4 per gallon = $63.63 per week = $3309.09 per year
- Third vehicle if household includes 1 child of driving age who drives to school/community college/other events.
50 miles per day @ 22 miles per gallon @ $4 per gallon = $63.63 per week = $3309.09 per year
$16,324.84 a year ($1360.30 per month) is a lot of money..
There are many work vehicles in the service industry that get worse than 15 mpg (including my truck). And there are many (most) who drive more than 100 miles per day. Obviously there are also people who can walk to work as well, or use mass transit..
What I'm trying to explain though, these service industry workers/buisness owners are mostly part of the lower middle class and gas prices are killing them. Most of them pay more for gas on a monthly basis then they pay on mortgage/rent.. Gas prices have a huge impact on the middle class