I used the south down stuff and yes it costs a lot less. But I didn't like the look of it in my tank. AndI would rather pay more to make my tank look better. I saved and added Nature's Ocean Live Bacterial sand for my entire bottom and seeded it with a detrivore kit. Looks much nicer, but yes the Southdown works, but it really sucks to change a deep sand bed in your tank if you don't like what it looks like.
peace
doug