I've been looking through Amazon and it's hard to tell if a binder contains pages or if they're sold separately. Also, it seems some binders are fixed (e.g, can't add more pages).
One of the requirements is that the binder has to have a decent picture of a pokemon on it and no picture of Ash.
I was out shopping earlier and I think I saw a Pokemon Black/White binder at a store (Toys-R-Us?) for $9 but I forget which one. On Ebay, some of the vendors are selling it for $20+ which seems high to me.
If you have a binder that you might want to sell, feel free to send me a PM.