That's an interesting link! However, like you said, you need specialized equipment to recycle it so this is not something that hobbyists or users of this machine will use since the cost will probably be more or less the same as the cost of a new bag of sand.
And you're still left with the huge amount of time it takes for it to cut steel. Commercial waterjet systems can cut that blade I mentioned in seconds. Wazer took 2 hours.
I think all these hobbyists and small shops that are considering this technology should beware of the cost. Suddenly, that seemingly high cost of commercial waterjet providers doesn't seem that high at all to me!
http://www.thefabricator.com/article/waterjetcutting/reusing...
(I guess it won't be worth setting up recycling for most users of this machine)
They say $0.30-$0.60 a pound (and I see lower prices suggested elsewhere), so the cost isn't astronomical.