$30K/mile for both sides of the interstate works out to about $2.84/foot if I did the math right. I assume it's typical barbed wire farm fencing and not extra high wildlife fencing and includes removal/disposal of the old fencing.
One opinion on the Internet states:
The typical barbed wire fence cost ranges from $1,345 to $6,075, with an average of $3,700. Barbed wire is dependable, sturdy, and affordable, costing $1 to $6 per linear foot, which makes it a popular choice for farms and livestock fencing.
My sister works at a farm and ranch supply store in Dickinson, ND, and I recall her talking about the scarcity of barbed wire during the pandemic.