Good advice from Bob. No point in wasting money on something you have to re-tension or that breaks in the middle of a match.
I don't know the particular ANSI steel numbers used (you could call to ask), but Nowlin makes their "Tuff Stuff" extractor by machining bar stock and also cryo-treats the finished part. Cryo-treating reduces the amount of set a spring takes, so it should be good for holding its tension well over the long term. Ed Brown makes a machined tool steel extractor that has a life time warranty. I have one of these, and it is plenty beefy and I have had no problems with it after probably 20,000 rounds through the particular gun it's in. There are other brands out there that I haven't tried, like NightHawk Custom, which is, again, machined steel, but this time with all the radiusing and polishing done, according to the description. All are in the ballpark of $30-$35 retail price at Brownells. You can pay more for fancier "systems", but I'm not sure I see the need. Properly fit, the good ones are quite satisfactory.