Tractor supply or farm stores sell them for around $8 for 40#. For our one coop that's 5'x12', it takes 4 bags to cover the floor a couple of inches. We do that in the spring, and don't touch it until next spring. By that time, about 75% of the pellets have turned to dustless sawdust. This is for approx 15 silkies, sometimes more or less.
We started using them in the brooders, and there's a game-changer. No more stinky brooders! The brooder stays dry as a bone, so no coccidiosis or anything else can start growing. Those I stir with my hand or a stick daily as their little feet don't scratch them around like the big chickens. (They start on paper towels their first couple of days, then I pull them and it's all pellets.)
You'll ask if the chickens or chicks eat them. Of course, they all have to try one, then drop it, and that's that. These are 100% pine. I do not wet them before using them, but I have heard a few that do. To me, that's wasting so much of the absorbative properties the pellets have, but to each their own. The sawdust they make is fluffy and dust-free, unlike normal sawdust.