Sioux Falls, SD (KELO-AM) - Triple A says holiday motorists are stretching the dollars further this Thanksgiving. The average price of unleaded gas in the state is $2.13...down 35 cents from just last month...and down a whopping 69 cents from last year! Sioux Falls has the cheapest prices averaging $1.84 / 9, out west in Rapid City is where you'll find the highest average punp price, with drivers paying $2.31. Other cities statewinde generally sit between $2.00 and $2.15 per gallon.