1 The cost for this type of mulch is about $10 per 2 cubic feet. 2  Oyster Shells-If you live in an area where oyster shells are readily available, they may be free for the taking. 3  They make a pretty mulch around plants, are semi-permeable and can also be used for paths and walkways. Rubber mulch also comes in a variety of colors to suit anyone's taste. 2  The cost for a bag of black or red rubber mulch is comparable to that of wood chips or nuggets-approximately $12 per 2-cubic feet. 3  Colored rubber mulch, such as purple or yellow, may be a few dollars more.