I have a variety (according to SWMBO - too LARGE a variety) of cast iron cookware. Most are Lodge and most of those were purchased new and pre-seasoned. I've found a few older Griswold pans at garage sales - they took some cleaning and re-seasoning, but are real champs.
I have found some great buys on Lodge at Fleet Farm (a chain in this area.) Look around you may find them in unexpected stores.
The pre-seasoning works -just be sure to clean them according to instructions and keep seasoning. One of the best things about cast iron is that the more you use them, the better they get. Some of my oldest most used pans are better than non-stick / Teflon.
And if you screw up - no worries - a good cleaning and re-seasoning will get you back on track.
IMHO short of finding an old Griswold the Lodge pre-seasoned is the best buy for cast iron. I do not suggest trying to save a dollar or two and ending up with a pitted, thin, unusable knock-off.
Good luck!
David