They're up more than 20 cents a gallon since Nov. 6, just as the holiday sales season was getting started. Whether those two or three extra bucks a tankful had any impact on consumer buying decisions in November and December is a debatable point - especially since higher gas prices earlier in 2006 had only a limited effect on the overall economy. And yet the price vulnerability among low-income workers is worth noting. For the week ended Dec. 25, an average gallon of self-serve regular in the Los Angeles area was $2.586, up from $2.549 a week earlier and $2.378 on Nov. 6. The federal government's weekly survey showed that SF and Seattle both had higher prices than L.A.