It's a little less expensive than a woven-wire fence to build and has about the same average lifespan of around 20 years, Edwards says. The estimated $1,947.75/quarter mile cost of a 5-wire barbed-wire fence takes into account the following: 1  4 8-inch wood posts ($28 apiece).2  57 4-inch wood posts ($9 apiece). 3  55 6 1/2-foot steel posts ($5 apiece).t's a little less expensive than a woven-wire fence to build and has about the same average lifespan of around 20 years, Edwards says. The estimated $1,947.75/quarter mile cost of a 5-wire barbed-wire fence takes into account the following: 1  4 8-inch wood posts ($28 apiece).