I just ***umed Harbor Freight's grit and gl*** bead prices would be lowest. Discovered a Tractor Supply in Leicester M*** close to 190 on 117 on the way home and stopped in to see if they carried small quan***ies of hard face arc welding rod. (They did) they had 50 lb bags of some kind of black coal slag abrasive grit for just 8$, and a 50# tub of 80 grit gl*** beads was $25. The coal slag got several 5 star reviews. One reviewer mentioned it is supposed to only last "once through" but he leaves it in his cabinet until it stops cutting. HF wants between 40 and 50 bucks for 44 lbs of their alumina grit, and 25# of 80 grit gl*** beads is between 28 and 30 bucks.
I use the coal slag in my blast cabinet, and also used it in my pressure pot outside. It seemed to work fine, and if ya got the time it can be swept up and strained and used again, but for $8.00 why bother. go for it.