I wouldn't pay $150 for that, and I doubt it weighs 150#.
For the same money, you can get a really nice chunk of mild steel or 4140 and have it shipped to your door. You don't need a horn, especially a square one, for 99% of any blacksmithing you might want to do. And if you do decide you want to make repeatable curls, you're better off bending around a section of pipe for uniformity.