Mooring equipment is very expensive, especially the lines. Unfortunately the lines limit what depth water one can anchor in. For example, a set of High Molecular Density Poly Ethelyne (HMDPE) lines for anchoring in 2500m of water costs approximately six million dollars - without the attachment hardware or anchors. These and other synthetic lines are the only real acceptable solution for deep water anchorages, as braided steel lines are too heavy and can corrode. In shallower water, however, the lines become proportionally cheaper.