Earlier quoted context omitted.
Even cheaper if you buy from a thrift store and put in some elbow grease. If you're an especially tool- and skill-rich hacker, then arc/stick welding with cast iron welding sticks can repair even lost causes. Of course, it isn't "cheap" by then, but any excuse to scratch that hacker/maker itch is fine by me.
I'm not really sure what welding has to do with any of this. A cast iron pan at Wal-Mart is roughly the same price as a non-stick skillet and will outlast it by decades. Even if you don't want the Wal-Mart brand, you can buy Lodge, which is respected enough even by cast iron fanatics, and is cheaper even than mid range non stick or aluminum/steel skillets.
If one is willing to perform possible repairs, they can prevent tossing out the original embedded energy cost of manufacturing and delivering the original cast iron product (and many other items), which if one is so inclined, makes choosing the non-gas stove option and re-gearing for it (assuming they have say, only ceramic cookware) for ecological reasons as one decision factor an even more energy-thrifty choice.
We throw away an astonishing amount of goods that in past generations would be repaired, because we heavily externalize the costs of doing so, since we're such a poor civilization in Banks' The Culture sense. Like externalizing the pipeline leak costs of supporting the gas infrastructure that sits behind the gas stove.