As @dculberson wrote, it’d be hard to find a decent $100 anvil in the US. Even a small 70lb anvil will run a few hundred dollars.
That being said, I’ve worked steel on railroadtrack-cum-anvil and it’s not easy. The top face of the rail is slightly curved, which makes hammering straight edges more difficult. I thought the guy in the video might make a cut along with face to level it out–that would have been very useful.
