I actually have a pretty decent set following that same method, spent way less than I could have too, (humble brag).
My advice if you're going that route:
Know what you want, it's easier to search for Ping i2's than filtering through a bajillion listings for "irons".
Be patient, the perfect deal will show up eventually.
Be ready, have cash on hand and be willing to go today if necessary.
Best deals tend to be in the off season. Never buy a motorcycle on a sunny day.
Good luck!
+Edit+ I freaking love my Ping i2 irons. The color system for club length is brilliant, they're crazy forgiving and really helped me step up my game. I've gone from hilariously bad to humorously bad.