I think what JwT meant was that you have to pay an added cost for any "expensive material or focus components" that the spell has when you create a knowstone. I don't have the magazine with me to check if that's true, but I agree with JwT that it shouldn't be. For example, if you make a knowstone of Stoneskin, which has a material component that costs 250gp per casting, the knowstone should still just cost (level squared) x 1000, and then whenever you use the knowstone to cast the spell, you have to supply the material component as usual.
Huh? What I understand of them is that they provide you with an _additional spell known_, nothing more. Material components, costly or otherwise, do not factor in. You use a sorcerer spell slot to cast the knowstone's spell, and if that spell requires any kind of material component then you have to provide it, as with _any other spell you cast_.
I like knowstones a lot, and find their price to my liking.