Anywhere there is a construction boom, there is stolen sand nearby.... especially near beaches. However, "Good" sand isn't just lying on the beach... most of that sand are bits of 'round' sand and tiny bits of shells.
Rounded sand doesn't make the best substrate for concrete; the best sand for concrete is more cubic and jagged, so it can set "harder". That's what I was talking about when I casually mentioned they'd done the research and found their sand is perfect quality for construction... which as it turns out, is actually very valuable!
Each SND token represents a cubic meter of that sand. Sand of that quality per cubic meter can fetch up to $5! Call your local 'sand' dealer and see how much they quote you for the same. (That's not to prove anything as much as it would be interesting to know).
(I know this is totally not technical, but I'm at work and don't have time to post links, I trust you can find news stories about stolen beach sand with a cursory websearch.)