You can easily season your own cast iron skillet. Basically, you put oil in a skillet and stick it in the oven for a half hour or so at 350 F; after you cook with it, clean it with a cloth and oil rather than a dishwasher. Every few months, oil it and throw it in a hot oven again.
Here's Martha Stewart's guide to dealing with cast iron: Cast Iron Pans - Martha Stewart Home & Garden (she's been to prison, and is a BAMF) You can find far more guides with a simple google search, but seasoning your own pan is easy.
You can season your own cast iron. Even if you buy it pre seasoned, you'll have to re-season it within a year. I'd to with the less expensive option.