We have 3 indoor-only cats and have chosen, for health and environmental reasons, to not use clay litter. We tried a bunch of other litters snd loved a corn-based brand called "world's best." Turns out, it's long-lasting but really expensive ($43 for 35 lbs; lasts us about a month).
I was researching options and found some online sources that suggested lay crumbles as an alternative. That's right - chicken feed. It's made from a grain base and has a similar texture. Our cats don't tend to eat their litter, so I wasn't too worried about other ingredients, but made sure the feed we got wasn't medicated. And at $14 for a 50 lb bag, it's waaay cheaper.
We've been using it for a month now and I'm satisfied. It smells different (like alfalfa) but clumps fine for easy scooping. The cats haven't had an issue with the change.
And now our cat litter is $0.28/lb, instead of $1.25.