100m was the selling price of the last one I saw.
I quickly decided it wasn't worth it. It would take forever to recoup the cost, before one even starts making profit. Figure, at best you get 5k per uncut diamond or analogous gem. Assuming you are able to get EVERY diamond you find up to 10k (you can't) and NEVER blow any up (you will, d100=1 is always out there ), that's 100,000,000/5000 == 20,000 uncut diamonds (or analogous gems) that you'd need to cover the cost of the chisel itself.
No thank you
Bard > chisel, for sure