In the current Christmas issue of Smokey mountain knife works and probably on their eknifeworks.com website, they have 12 packs of frost cutlery folders for $19.99.
I doubt you'll find anything cheaper, and having had some of these particular knives I know they're capable of taking an edge which is important for sharpening practice.
I would recommend a supporting dealer, but I doubt they have this stuff and they're not loosing business when you just want dirt cheap knives to practice on before going to their websites to buy good knives to actually use.