Pine shavings would be hundreds of dollars to cover my 96 sq ft run a few inches deep. The bags at our local store are pretty expensive.
Really? Here a bag of pine shavings is $5-$6 or so and covers 64 sq ft. I know because a bag will cover my small 8x4 coop floor twice. Buy it at a feed store or other place that sells livestock supplies, not the pet section in smaller stores or walmart.
Pine dries out faster than straw so it is less of a mold risk. Also find a local gardener, they would be happy to take bags of used straw for their gardens.