The price tag for a gallon of regular gas at some Greenwich stations is reaching new heights. At the Shell Station on West Putnam Avenue in Greenwich a gallon of gas costs more than $3, while the rest of southwestern Connecticut is still seeing prices between $2.69 and $3. Some say the rising prices could soon be the case across southwestern Connecticut. University of Connecticut Economics Professor William Alpert says the prices may trigger a change in how much gas people buy and other shopping habits. Some discount chains like WalMart are making changes to reflect anticipated changes in people's buying habits, offering more store brands, which tend to be cheaper. Related Story