Freight is based on weight and volume and distance.
Yes, cost does go up the further it has to travel. Across town or maybe in state might be cheaper but you want to cover your bases as you don't know where your going to have to ship them.
My calculation was from here, Tulsa, to Seattle, WA.
Don't forget the packaging. This will add bulk and weight.
Another option is to have the buyer cover and arrange freight. Basically, you would give the seller the weights and dims and the pick up address and they would arrange a pick up by whatever freight carrier they choose. This puts freight logistics and cost into the buyers hands and frees you of headaches and possible lost monies. However, most people (buyers) don't like this as they can't just push the easy button.