On another altis life server, where are shipwrecks, they do the following:
They added some new items , like " old jar " , " rusty box " , " old gold bar " and like 10-15 stuff like these. Each of them has a differenct price from $250 to $10.000. And once you start to use your excavator on the shipwreck, they pop up in random order ( basically just like when u go out fishing with your boat ). Then you can remove everything what is cheap, and mine for more what is expensive. how bout this ?