I recently built an entrance wall. The prices quoted were crazy so I attempted it myself. The walls are around 80 sq meters with 4 piers. I borrowed a tractor and trailer and went to the local John A Woods quary and with help picked about 20 ton of nicely shaped limestone. This took about a day and a half. I made a good start at the wall but having a two year old 'helping' all the time made the going slow. In the end I got three Polish guys who work for a local builder to finish it.
Cost (approx)
stone - 350, Tools - 100,cement - 250ish, labour - 2700, sand - 250, time -alot, sweat - alot
So it cost less than four grand and looks good. A bit sressful but I saved the price of a good holiday.