Dominick Reuter/Business Insider Average gas prices above $4.50 a gallon are prompting more drivers to fill up at warehouse clubs like Costco. The company saw a 3% boost in comparable fuel sales last month. Increased traffic at the pump can also draw customers into the store, where sales are up. A rising tide may lift all boats, but rising gas prices only lift a few. Costco is increasingly looking like a winner during this round of high fuel costs as US consumers look for ways to balance their weekly budgets. The US average price of a gallon of regular gas has remained above $4 for a month — topping $4.50 this week — leading more drivers to fill up at warehouse clubs like Costco. Those numbers are translating into a top-line boost for Costco, which saw 11.7% US comparable sales growth last month, of which 3 percentage points were from fuel sales.…