Not a dungeon per se, but my games club owns a Blood Bowl pitch made up fo 1 inch square stone mosaic tiles which one of the members, who worked for a whole sale hardware place at the time, got cheap. It weighs a ton, but it looks fantastic. Being made up of individual tiles means I cannot comment on the laser-etching of stone idea.
That's a cool idea! I've been trying to come up with a good way to do a non-cardboard DungeonBowl board.