50% ... but of what?

I've now seen that fashionably scruffy guy driving his Cadillac Escalade hybrid one too many times. The commercial says it has 50% better city mpg. Yeah, just about - maybe even better. The regular one gets 12 mpg in the city. The hybrid gets 18 or 20, depending which site you look at. Of course the gas-powered one gets 20 highway, and the hybrid gets 21. Plus, the hybrid costs over $71,000 as compared to the gas version, which costs a mere $68,000...

I suppose if you must have one of those monsters, the hybrid version is better than the other. But talk about the lesser of evils...