The English CCS artbooks were produced by the late TOKYOPOP and a quick scan of eBay shows them selling as low as $8. The original Japanese art books that cover the manga and the oversized anime artbooks for the most part run between $15-$30. The CLAMP no kiseki issues #1 and 2 which contain CCS art generally are dirt cheap, about $5 minus the chess pieces though I've seen a couple of seaked ones including the chess pieces for about $10/ $15. Note the prices don't include shipping.