Haha, that is completely untrue. He has given me a range of coin ammounts (ranging from like 16gp to 600gp) and lots of saphires, emeralds, rubies (i think), and thats about it I think. Im sure there are many other things he gives.
I saw in one of your guides that you didn't have rock crabs in there, but they do. (I think rock crabs are lvl 13?) I got a clue from one a few days ago, just doing it now.
Would make runescape much much too easy :) Miners wouldnt have to bank and neither would anyone else that collect resources. Nice idea, I like it, but it is not reasible.