The problem is that when you're dealing with weddings, NOTHING is cheap.
The NEXT problem is that you're looking for something specific. The more generic your search, the more likely you are to find it for a reasonable price.
That being said, this site has quite a few ideas for favors at reasonable, if not CHEAP prices.
Cinderella / Princess Theme Weddings | Favor Ideas
You didn't really give a price range for cheap, and I am not sure how many you'll need, but you can always get creative and MAKE favors as well.....a poem printed on card stock with glitter set by each plate isn't a BAD favor, just not a fancy one.