Iirc, blasting sand is even less expensive and it comes in different grit sizes. In our area, it's close to pure and doesn't add to TDS. Forbes had told me in the past that the stuff around Los Angeles was nasty & couldn't be used. Due to weight, much of this stuff is typically sourced locally.....for $2.41. It's supposed to be used around fireplaces, but I know an alternative use....
I use the "Washed Play Sand" from Home Depot. It's silica sand. It can be dusty, and I even use it without washing it. It works fine for me.
-Hermes.