If you really want to know how much different parts of landscaping cost, then take a look at this book. From hardscape to plants to grading...it's all there. Based on my 15 years experience! Up to date as of January 2012. $19.95
Accepting the FREE evaluation from at least two or three landscape design service specialists is a good way to get a ball park figure on the costs and also to know the landscape design possibilities on your property.