Prime's about what, $7 a month? Each mile I drive costs $0.20 in gas. If having Prime saves me just half an hour / 35 mi of driving a month (less than two trips

Prime's about what, $7 a month? Each mile I drive costs $0.20 in gas. If having Prime saves me just half an hour / 35 mi of driving a month (less than two trips to Walmart), it's cheaper than going to the store.