I dont know how this compares to other peoples yearly expense, but we've been using Worlds Best Cat Litter which is a flushable litter made from corn. It does clump and we use it with the Omega Paw self cleaning litter box and last year our litter cost for 1 cat was only $80. I buy the litter from
amazon for $38 for a 34 pound bag. We only used 2 bags last year with our one cat. I think the litter combined with the litter box we use, uses less litter. Here is the litter box I am referring to ( i LOVE this litter box!):
http://www.amazon.com/Omega-Self-Cl...?ie=UTF8&s=home-garden&qid=1278611247&sr=8-14
We have amazon prime so I dont pay extra for the shipping. Not sure how much the shipping cost but I do know they sell this litter at PetCo.