Unfortunately both parts of your comment are incorrect.
Upper class Americans and Europeans generate more emissions per capita than lower / middle class people. They consume more, so they emit more.
I don't know your specific situation, but in general the carbon offsets you buy aren't actually priced to the real cost of reduction, and your estimate of your carbon footprint is likely low. So the real price would likely be significantly higher. If you're living in a large (and so heat / cooling efficient) building in the bay area where those costs are minimized anyway, and don't have a car, then you're an outlier, and you can't extrapolate accurately from your situation.
Sure, they generate more, but the lower/middle class Westerners can't afford what they generate but the rich guys can.
The price of the offset doesn't matter because for climate change locality effects are not big on this scale. I double the estimate from Terrapass so I'm pretty certain it's good.
Upper class Americans and Europeans generate more emissions per capita than lower / middle class people. They consume more, so they emit more.
I don't know your specific situation, but in general the carbon offsets you buy aren't actually priced to the real cost of reduction, and your estimate of your carbon footprint is likely low. So the real price would likely be significantly higher. If you're living in a large (and so heat / cooling efficient) building in the bay area where those costs are minimized anyway, and don't have a car, then you're an outlier, and you can't extrapolate accurately from your situation.